AN ABSTRACT OF THE DISSERTATION OF Priya Londhe, for the Doctor of Philosophy degree in Biochemistry and Molecular Biology, presented on 30th July, 2013 at Southern Illinois University Carbondale. TITLE: UNRAVELING THE MOLECULAR MECHANISMS OF THE CLASS II TRANSACTIVATOR IN SKELETAL MUSCLE MAJOR PROFESSOR: Dr. Judy Davie The inflammatory cytokine, interferon gamma, IFN-gamma orchestrates a diverse array of fundamental physiological processes and exhibits complex effects on myogenesis. IFN-gamma also induces the class II transactivator, CIITA, which is a critical mediator of IFN-gamma mediated repression and activation. The aims in my dissertation are directed towards understanding the role of IFN-gamma and CIITA in muscle. Stimulation by IFN-gamma in skeletal muscle cells induces CIITA expression as well as MHC class II gene expression. We show that the IFN-gamma induced inhibition of myogenesis is mediated by CIITA, which specifically interacts with myogenin. CIITA acts by both, repressing the expression and inhibiting the activity of myogenin at different stages of myogenesis. The IFN-gamma mediated repression is reversible, with myogenesis proceeding normally upon removal of IFN-gamma. We also show that CIITA is indispensible for the inhibition of myogenesis. To gain a mechanistic insight into the IFN-gamma induced repression of myogenesis, we have discovered that IFN-gamma and CIITA inhibit myogenesis by modifying gene regulation in a muscle cell subject to inflammation. We show that CIITA first interacts with JARID2, a non catalytic subunit of PRC2 complex, which induces a paused RNAPII, phosphorylated at serine 5 and then interacts with the catalytic subunit EZH2, in a JARID2 dependent manner. Our data show that both CIITA and IFN-gamma block myogenesis by the induction and recruitment of the PRC2 complex, which is normally silenced in a differentiating muscle cell. One of my dissertation aims sheds light on the silencing of CIITA in Rhabdomyosarcoma. Silencing of CIITA prevents the expression of MHC Class I and II genes. We have found that IFN-gamma signaling is intact in these cells, but pSTAT1 and IRF1 do not bind to the CIITA PIV promoter. The CIITA promoter is not hypermethylated in RD (ERMS) cells, but shows a modestly enhanced methylation status in SJRH30 (ARMS) cells. We have also observed that histone acetylation, which normally increases on the CIITA PIV promoter following IFN-gamma treatment, is blocked in both types of RMS cells. Further, our studies also impart a novel role for IFN-gamma and CIITA in inhibiting the IGF induced activation of muscle specific genes. Our data show that IFN-gamma does not block the signaling cascade of IGF. However, blocking exogenous IFN-gamma restores IGF activation of muscle specific genes. My dissertation also reveals an important role for the FACT complex in the early steps of gene activation through its histone chaperone activities that serve to open chromatin structure and facilitate transcription promoting muscle differentiation. We show that myogenin interacts with the FACT complex and the recruitment of FACT complex to muscle specific genes is dependent on myogenin. The final aim in my dissertation highlights the distinct binding profiles of the MRFs and E proteins during proliferation and differentiation. Our sequential ChIP assays show that MYOD, MYOG, and MYF5 co-occupy promoters. Taken together, my dissertation provides a comprehensive understanding of the molecular mechanisms during myogenesis and reveals the deleterious effects of chronic inflammation in skeletal muscle.

The precise regulation of Major Histocompatibility class II (MHC-II) genes plays an important role in the control of the adaptive immune response. MHC-II genes are expressed constitutively in only a few cell types, but their expression can be induced by the inflammatory response cytokine interferon gamma (INF-γ). The regulation of MHC-II is controlled by a Master Regulator, the class II transactivator (CIITA). Multiple studies have shown that CIITA regulated expression of MHC-II is controlled and induced by INF-γ. It has been also shown that a functional CIITA gene is necessary for the expression of MHC-II genes. CIITA is thus a general regulator of both constitutive and inducible MHC-II expression. Although much is known about the transcription factors necessary for CIITA expression, there is little information as to the epigenetic modifications and the requisite enzymes needed to provide these transcription factors access to DNA. Previous studies in the Greer lab have shown that increased levels of acetylation of histones H3 upon INF-γ stimulation, as does tri-methylation of H3K4 upon prolonged cytokine stimulation. Similar observations were made at early time points post IFN-γ stimulation, where there is an instantaneous increase in the levels of H3K18ac and H3K4me3. In contrast to this, the levels of silencing modifications begin to drop with in the first 20 minutes of IFN-γ stimulation. The binding of STAT1 reaches its peak at about 60 minutes and the first transcripts for the protein start to appear as early as 40 minutes post the cytokines stimulation. Our study is the first to link the rapidly occurring epigenetic changes at the CIITA promoter pIV to EZH2

It is evident that components of the 26S proteasome function beyond protein degradation in the regulation of transcription. Studies in yeast implicate the 26S proteasome, specifically the 19S cap, in the epigenetic regulation of transcription. Saccharomyces cerevisiae 19S ATPases remodel chromatin by facilitating histone acetylation and methylation. However, it is unclear if the 19S ATPases play similar roles in mammalian cells. We previously found that the 19S ATPase Sug1 positively regulates transcription of the critical inflammatory gene MHC-II and that the MHC-II promoter fails to efficiently bind transcription factors upon Sug1 knockdown. MHC-II transcription is regulated by the critical coactivator CIITA. We now find that Sug1 is crucial for regulating histone H3 acetylation at the cytokine inducible MHC-II and CIITA promoters. Histone H3 acetylation is dramatically decreased upon Sug1 knockdown with a preferential loss occurring at lysine 18. Research in yeast indicates that the ortholog of Sug1, Rpt6, acts as a mediator between the activating modifications of histone H2B ubiquitination and H3 methylation. Therefore, we characterized the role the 19S proteasome plays in regulating additional activating modifications. As with acetylation, Sug1 is necessary for proper histone H3K4 and H3R17 methylation at cytokine inducible promoters. In the absence of Sug1, histone H3K4me3 and H3R17me2 are substantially inhibited. Our observation that the loss of Sug1 has no significant effect on H3K36me3 implies that Sug1’s regulation of histone modifications is localized to promoter regions as H3K4me3 but not H3K36me3 is clustered around gene promoters. Here we show that multiple H3K4 histone methyltransferase subunits bind constitutively to the inducible MHC-II and CIITA promoters and that over-expressing one subunit significantly enhances promoter activity. Furthermore, we identified a critical subunit of the H3K4 methyltransferase complex that binds multiple histone modifying enzymes, but fails to bind the CIITA promoter in the absence of Sug1, implicating Sug1 in recruiting multi-enzyme complexes responsible for initiating transcription. Finally, Sug1 knockdown maintains gene silencing as elevated levels of H3K27 trimethylation are observed upon Sug1 knockdown. Together these studies strongly implicate the 19S proteasome in mediating the initial reorganization events to relax the repressive chromatin structure surrounding inducible genes.

Major Histocompatibility Complex (MHC) class II molecules are indispensable arms of the im-mune system that present extracellular antigens to CD4+T cells and initiate the adaptive immune response. MHC class II expression requires recruitment of a master regulator, the class II trans-activator (CIITA). How this master transcriptional regulator is recruited, stabilized and degraded is unknown. The 26S proteasome, a master regulator of protein degradation, is a multi-subunit complex composed of a 20S core particle capped on one or both ends by 19S regulatory particles. Previous findings have linked CIITA and MHC class II transcription to the ubiquitin proteasome system (UPS) as mono-ubiquitination of CIITA increases its transactivity whereas poly-ubiquitination targets CIITA for degradation. Increasing evidence indicates individual ATPase subunits of the 19S regulator play non-proteolytic roles in transcriptional regulation and histone modification. Our initial observations indicate proteasome inhibition decreases CIITA transac-tivity and MHC class II expression without affecting CIITA expression levels. Following cyto-kine stimulation, the 19S ATPase Sug1 associates with CIITA and with the MHC class II enhan-ceosome complex. Absence of Sug1 reduces promoter recruitment of CIITA and proteasome inhibition fails to restore CIITA binding, indicating Sug1 is required for CIITA mediated MHC class II expression. Furthermore, we identify a novel N-terminal 19S ATPase binding domain (ABD) within CIITA. The ABD of CIITA lies within the Proline/Serine/Threonine (P/S/T) re-gion of CIITA and encompasses a majority of the CIITA degron sequence. Absence of the ABD increases CIITA half-life, but blocks MHC class II surface expression, indicating that CIITA requires interaction with the 19S ATPases for both its deployment and destruction. Finally, we identify three degron proximal lysine residues, lysines (K): K315, K330 and K333, and a phosphorylation site, serine (S), S280, located within the CIITA degron, that regulate CIITA ubiquitination, stability and MHC class II expression. These are the first lysine residues identified as sites of CIITA ubiquitination that are essential for MHC class II expression. These observations increase our understanding of the role of the UPS in modulating CIITA mediated MHC class II transcription and will facilitate the development of novel therapies involving manipulation of MHC class II gene expression.

Major Histocompatibility Complex Class-II (MHC-II) molecules are critical regulators of adaptive immunity that present extracellular antigens required to activate CD4+ T cells. MHC-II are regulated at the level of transcription by master regulator, the Class II Transactivator (CIITA), whose association with the MHC-II promoter is necessary to initiate transcription. Recently, much research focused on novel mechanisms of transcriptional regulation of critical genes like MHC-II and CIITA; findings that the macromolecular complex of the 26S-proteasome is involved in transcription have been perhaps the most exciting as they impart novel functions to a well studied system. Proteasome is a multi-subunit complex composed of a 20S-core particle capped by a 19S-regulatory particle. The 19S contains six ATPases which are required for transcription initiation and elongation. We demonstrate that 19S ATPase-S6a inducibly associates with CIITA promoters. Decreased expression of S6a negatively impacts recruitment of the transcription factors STAT-1 and IRF-1 to the CIITA due to significant loss in histone H3 and H4 acetylation. S6a is robustly recruited to CIITA coding regions, where S6a binding coordinates with that of RNA polymerase II. RNAi mediated S6a knockdown significantly diminishes recruitment of Pol II and P-TEF-b components to CIITA coding regions, indicating S6a plays important roles in transcriptional elongation. Our research is focused on the ways in which accessibility to and transcription of DNA is regulated. While cancers are frequently linked to dysregulated gene expression, contribution of epigenetics to cancers remains unknown. To achieve metastatic ability, tumors alter gene expression to escape host immunosurveilance. MHC-II and CIITA expression are significantly downregulated in highly metastatic MDA-MB-435 breast cancer cells. This suppression correlates with elevated levels of the silencing modification H3K27me3 at CIITA and a significant reduction in Pol II recruitment. We observe elevated binding of the histone methyltransferase to CIITApIV and demonstrate this enzyme is a master regulator of CIITA gene expression. EZH2 knockdown results in significant increases in CIITA and MHC-II transcript levels in metastatic cells. In sum, transcriptional regulation by the 19S-proteasome and histone modifying enzymes represents novel mechanisms of control of mammalian gene expression and present novel therapeutic targets for manipulating MHC expression in disease.

It is evident that components of the 26S proteasome function beyond protein degradation in the regulation of transcription. Studies in yeast implicate the 26S proteasome, specifically the 19S cap, in the epigenetic regulation of transcription. Saccharomyces cerevisiae 19S ATPases remodel chromatin by facilitating histone acetylation and methylation. However, it is unclear if the 19S ATPases play similar roles in mammalian cells. We previously found that the 19S ATPase Sug1 positively regulates transcription of the critical inflammatory gene MHC-II and that the MHC-II promoter fails to efficiently bind transcription factors upon Sug1 knockdown. MHC-II transcription is regulated by the critical coactivator CIITA. We now find that Sug1 is crucial for regulating histone H3 acetylation at the cytokine inducible MHC-II and CIITA promoters. Histone H3 acetylation is dramatically decreased upon Sug1 knockdown with a preferential loss occurring at lysine 18. Research in yeast indicates that the ortholog of Sug1, Rpt6, acts as a mediator between the activating modifications of histone H2B ubiquitination and H3 methylation. Therefore, we characterized the role the 19S proteasome plays in regulating additional activating modifications. As with acetylation, Sug1 is necessary for proper histone H3K4 and H3R17 methylation at cytokine inducible promoters. In the absence of Sug1, histone H3K4me3 and H3R17me2 are substantially inhibited. Our observation that the loss of Sug1 has no significant effect on H3K36me3 implies that Sug1’s regulation of histone modifications is localized to promoter regions as H3K4me3 but not H3K36me3 is clustered around gene promoters. Here we show that multiple H3K4 histone methyltransferase subunits bind constitutively to the inducible MHC-II and CIITA promoters and that over-expressing one subunit significantly enhances promoter activity. Furthermore, we identified a critical subunit of the H3K4 methyltransferase complex that binds multiple histone modifying enzymes, but fails to bind the CIITA promoter in the absence of Sug1, implicating Sug1 in recruiting multi-enzyme complexes responsible for initiating transcription. Finally, Sug1 knockdown maintains gene silencing as elevated levels of H3K27 trimethylation are observed upon Sug1 knockdown. Together these studies strongly implicate the 19S proteasome in mediating the initial reorganization events to relax the repressive chromatin structure surrounding inducible genes.

Major histocompatibility complex molecules (MHCII) are cell surface glycoproteins that present extracellular antigens to CD4+ T lymphocytes and initiate adaptive immune responses. Apart from their protective role, overexpression of MHCII contributes to autoimmune disorders where the immune system attacks our own tissues. Autoimmune diseases are characterized by self-reactive responses to autoantigens, promoting tissue damage, inflammation mediated by proinflammatory cytokines, autoreactive lymphocytes, and autoantibodies. MHCII molecules are tightly regulated at the level of transcription by Class II transactivator (CIITA). CIITA associates with an enhanceosome complex at MHCII promoters and regulates the expression of MHCII. It is thus crucial to understand the regulation of CIITA expression in order to regulate MHCII in autoimmune diseases. Our lab has shown that the 19S ATPases of the 26S proteasome associate with MHCII and CIITA promoters and play important roles in gene transcription, regulate covalent modifications to histones, and are involved in the assembly of activator complexes in mammalian cells. The mechanisms by which the proteasome influences transcription remain unclear. Here, we define novel roles of the 19S ATPases Sug1, S7, and S6a in expression of CIITApIV genes. These ATPases are recruited to CIITApIV promoters and coding regions, interact with the elongation factor PTEFb, and with Ser5 phosphorylated RNA Pol II. Both the generation of CIITApIV transcripts and efficient recruitment of RNA Pol II to CIITApIV are negatively impacted by knockdown of 19S ATPases. Alternatively, inflammation is also suppressed via the Regulator of G-protein signaling 10 (RGS10) in microglial cells which express high levels of RGS10 and promote homeostasis in the central nervous system. However, chronic activation of microglial cells leads to release of cytokines which cause neuroinflammation. Our investigation of roles played by RGS10 in chronically activated microglial cells indicates that RGS10 binds to promoters of IL-1β, and TNF-α and regulates these genes, while the molecular mechanism remains to be investigated. Together, our observations indicate roles for the UPS in modulating gene expression and for RGS10 in regulating proinflammatory cytokines in microglial cells, each of which provides novel therapeutic targets to combat inflammation in autoimmune and neurodegenerative diseases.

O fator CIITA é a proteína responsável por controlar a transcrição de genes do complexo principal de histocompatibilidade de classe II (MHC II) envolvidos na apresentação antigênica a linfócitos T CD4+. A expressão desta proteína é complexa e célula-específica, dependendo de mecanismos de regulação transcricionais e póstranscricionais. Com o intuito de investigar o potencial do fator CIITA como adjuvante molecular, no presente estudo desenvolvemos e validamos sistemas de transferência gênica capazes de promover a eficiente expressão de CIITA em vários tipos celulares. Além disso, investigamos a regulação pós-traducional deste fator em células não hematopoéticas. Desta forma, foram produzidos um vetor plasmidial e um vetor lentiviral, ambos carreando a sequência do fator CIITA humano desenhada in silico visando a eliminação de elementos cis-reguladores, e otimizada para eficiente expressão em células humanas. A transfecção/transdução de três linhagens de células humanas não hematopoéticas resultou na eficiente expressão de CIITA com localização nuclear apropriada. Células expressando CIITA apresentaram síntese de novo do MHC II, confirmando a funcionalidade da proteína e validando ambos os vetores para a análise futura da atividade adjuvante do CIITA em imunizações gênicas. Ensaios preliminares de inoculação de explantes de pele humana com o vetor lentiviral evidenciaram a eficiente transdução e expressão do CIITA exógeno em células primárias. Em seguida, células dendríticas (DCs) derivadas de monócitos de indivíduos saudáveis ou infectados com HIV-1 foram transduzidas com o vetor lentiviral para confirmar a expressão do CIITA em células primárias e avaliar a aplicação desse sistema adjuvante no aprimoramento da vacina de DCs anti-HIV. DCs de indivíduos saudáveis ou infectados foram transduzidas com sucesso pelo lentivírus, o qual induziu uma produção prolongada do mRNA codificando CIITA. Entretanto, os vetores lentivirais induziram um aumento inespecífico da expressão de marcadores fenotípicos das DCs, incluindo as moléculas do MHC II, o que impediu a avaliação indireta da expressão e atividade do fator CIITA através da detecção da expressão aumentada do MHC II. Ensaios futuros irão avaliar se o fator transcricional é expresso pelas DCs transduzidas ou se essas células apresentam um controle mais restrito da expressão do CIITA comparadas às linhagens celulares avaliadas. Interessantemente, ensaios de western blot comparativos entre as três linhagens de células humanas transfectadas/transduzidas, juntamente com ensaios de inibição da degradação protéica pelo inibidor do proteassoma, nos permitiu descrever um novo mecanismo de regulação pós-traducional do CIITA. Aqui, nós identificamos que cada tipo de célula não hematopoética mantém níveis específicos da proteína, e portanto, da sua atividade transcricional, através da regulação da degradação do CIITA pelo proteassoma. Essa regulação é mediada pela modulação dos níveis das proteínas da leucemia promielocítica (PML) acopladas a proteínas SUMO (modificadores pequenos similares à ubiquitina), modificação pós-traducional requerida para a interação PML-CIITA que impede a degradação pelo proteassoma. Esse novo mecanismo aqui descrito contribui para o entendimento ainda incipiente da regulação pós-traducional do fator CIITA em células não hematopoéticas e pode ter implicações importantes na aplicação dessa proteína como adjuvante molecular para imunoterapias / The CIITA factor is a protein responsible for controlling the transcription of major histocompatibility complex class II (MHC II) genes involved on antigen presentation to CD4+ T helper cells. The expression of this transcription factor is complex and differs in various cell types depending on transcriptional and post-transcriptional regulatory mechanisms. In order to investigate the CIITA factor potential as molecular adjuvant, here we developed and validated two gene delivery systems capable of promoting efficient CIITA expression in various human cell types. Additionally, we applied the delivery systems to investigate the post-translational regulation of this factor in nonimmune cells. A DNA plasmid and a lentiviral vector were produced, both carrying the human CIITA DNA sequence in silico designed to avoid cis-regulatory elements, and genetic optimized for expression efficacy in human cells. Transfection or transduction of three different non-immune human cell lines resulted in efficient CIITA expression with proper nuclear localization. The CIITA-expressing cells presented de novo MHC II molecules expression confirming the functionality of the exogenous protein, and validating both delivery systems for the future analysis of the CIITA adjuvant activity in genetic immunizations. Preliminary assays involving the inoculation of the lentiviral vector into human skin explants showed efficient transduction and expression of exogenous CIITA in primary cells. Next, monocyte-derived dendritic cells (DCs) from healthy individuals and HIV-1-infected patients were transduced with the lentiviral vector to confirm the exogenous CIITA expression in primary human cells and also evaluate the applicability of this adjuvant system to improve the DC-based vaccines against HIV. DCs from healthy and infected individuals were successfully transduced by the lentivirus, which induced a sustained CIITA mRNA production. However, the vector particles by themselves induced an unspecific upregulation of DC`s phenotypic surface markers, including the MHC II molecules, impairing our strategy to indirectly evaluate CIITA expression and activity through the detection of MHC II enhanced expression. Further investigations are necessary to confirm whether the transcription factor is efficiently expressed in transduced DCs or if these cells present a more restrict control of CIITA protein expression than the evaluated non-immune cells. Interestingly, western blot assays comparing the three human cell lines, transfected or transduced, along with inhibition of protein degradation by proteasome inhibitor treatments, allowed us to describe a new and intricate mechanism of CIITA post-translational regulation. Here we identified that each non-immune cell type maintain specific protein levels, and hence transcriptional activity, by modulating the rate of CIITA proteasomal degradation. This modulation is achieved by controlling the levels of Promyelocytic Leukemia (PML) proteins attached to Small Ubiquitin-like Modifier (SUMO) proteins, a post-translational modification required for the PML-CIITA interaction, which impairs the proteasomal degradation. This new mechanism described here contributes to the developing understanding of the CIITA post-translational regulation in non-immune cells, and might have important implications in the use of this transcription factor as a molecular adjuvant for immunotherapies

O fator CIITA é a proteína responsável por controlar a transcrição de genes do complexo principal de histocompatibilidade de classe II (MHC II) envolvidos na apresentação antigênica a linfócitos T CD4+. A expressão desta proteína é complexa e célula-específica, dependendo de mecanismos de regulação transcricionais e póstranscricionais. Com o intuito de investigar o potencial do fator CIITA como adjuvante molecular, no presente estudo desenvolvemos e validamos sistemas de transferência gênica capazes de promover a eficiente expressão de CIITA em vários tipos celulares. Além disso, investigamos a regulação pós-traducional deste fator em células não hematopoéticas. Desta forma, foram produzidos um vetor plasmidial e um vetor lentiviral, ambos carreando a sequência do fator CIITA humano desenhada in silico visando a eliminação de elementos cis-reguladores, e otimizada para eficiente expressão em células humanas. A transfecção/transdução de três linhagens de células humanas não hematopoéticas resultou na eficiente expressão de CIITA com localização nuclear apropriada. Células expressando CIITA apresentaram síntese de novo do MHC II, confirmando a funcionalidade da proteína e validando ambos os vetores para a análise futura da atividade adjuvante do CIITA em imunizações gênicas. Ensaios preliminares de inoculação de explantes de pele humana com o vetor lentiviral evidenciaram a eficiente transdução e expressão do CIITA exógeno em células primárias. Em seguida, células dendríticas (DCs) derivadas de monócitos de indivíduos saudáveis ou infectados com HIV-1 foram transduzidas com o vetor lentiviral para confirmar a expressão do CIITA em células primárias e avaliar a aplicação desse sistema adjuvante no aprimoramento da vacina de DCs anti-HIV. DCs de indivíduos saudáveis ou infectados foram transduzidas com sucesso pelo lentivírus, o qual induziu uma produção prolongada do mRNA codificando CIITA. Entretanto, os vetores lentivirais induziram um aumento inespecífico da expressão de marcadores fenotípicos das DCs, incluindo as moléculas do MHC II, o que impediu a avaliação indireta da expressão e atividade do fator CIITA através da detecção da expressão aumentada do MHC II. Ensaios futuros irão avaliar se o fator transcricional é expresso pelas DCs transduzidas ou se essas células apresentam um controle mais restrito da expressão do CIITA comparadas às linhagens celulares avaliadas. Interessantemente, ensaios de western blot comparativos entre as três linhagens de células humanas transfectadas/transduzidas, juntamente com ensaios de inibição da degradação protéica pelo inibidor do proteassoma, nos permitiu descrever um novo mecanismo de regulação pós-traducional do CIITA. Aqui, nós identificamos que cada tipo de célula não hematopoética mantém níveis específicos da proteína, e portanto, da sua atividade transcricional, através da regulação da degradação do CIITA pelo proteassoma. Essa regulação é mediada pela modulação dos níveis das proteínas da leucemia promielocítica (PML) acopladas a proteínas SUMO (modificadores pequenos similares à ubiquitina), modificação pós-traducional requerida para a interação PML-CIITA que impede a degradação pelo proteassoma. Esse novo mecanismo aqui descrito contribui para o entendimento ainda incipiente da regulação pós-traducional do fator CIITA em células não hematopoéticas e pode ter implicações importantes na aplicação dessa proteína como adjuvante molecular para imunoterapias / The CIITA factor is a protein responsible for controlling the transcription of major histocompatibility complex class II (MHC II) genes involved on antigen presentation to CD4+ T helper cells. The expression of this transcription factor is complex and differs in various cell types depending on transcriptional and post-transcriptional regulatory mechanisms. In order to investigate the CIITA factor potential as molecular adjuvant, here we developed and validated two gene delivery systems capable of promoting efficient CIITA expression in various human cell types. Additionally, we applied the delivery systems to investigate the post-translational regulation of this factor in nonimmune cells. A DNA plasmid and a lentiviral vector were produced, both carrying the human CIITA DNA sequence in silico designed to avoid cis-regulatory elements, and genetic optimized for expression efficacy in human cells. Transfection or transduction of three different non-immune human cell lines resulted in efficient CIITA expression with proper nuclear localization. The CIITA-expressing cells presented de novo MHC II molecules expression confirming the functionality of the exogenous protein, and validating both delivery systems for the future analysis of the CIITA adjuvant activity in genetic immunizations. Preliminary assays involving the inoculation of the lentiviral vector into human skin explants showed efficient transduction and expression of exogenous CIITA in primary cells. Next, monocyte-derived dendritic cells (DCs) from healthy individuals and HIV-1-infected patients were transduced with the lentiviral vector to confirm the exogenous CIITA expression in primary human cells and also evaluate the applicability of this adjuvant system to improve the DC-based vaccines against HIV. DCs from healthy and infected individuals were successfully transduced by the lentivirus, which induced a sustained CIITA mRNA production. However, the vector particles by themselves induced an unspecific upregulation of DC`s phenotypic surface markers, including the MHC II molecules, impairing our strategy to indirectly evaluate CIITA expression and activity through the detection of MHC II enhanced expression. Further investigations are necessary to confirm whether the transcription factor is efficiently expressed in transduced DCs or if these cells present a more restrict control of CIITA protein expression than the evaluated non-immune cells. Interestingly, western blot assays comparing the three human cell lines, transfected or transduced, along with inhibition of protein degradation by proteasome inhibitor treatments, allowed us to describe a new and intricate mechanism of CIITA post-translational regulation. Here we identified that each non-immune cell type maintain specific protein levels, and hence transcriptional activity, by modulating the rate of CIITA proteasomal degradation. This modulation is achieved by controlling the levels of Promyelocytic Leukemia (PML) proteins attached to Small Ubiquitin-like Modifier (SUMO) proteins, a post-translational modification required for the PML-CIITA interaction, which impairs the proteasomal degradation. This new mechanism described here contributes to the developing understanding of the CIITA post-translational regulation in non-immune cells, and might have important implications in the use of this transcription factor as a molecular adjuvant for immunotherapies