Two types mechanisms that control gene expression involve cis-regulatory factors and trans-regulatory factors. Cis-acting regulatory RNAs include targeted messenger RNA (mRNA) specificity and AU-rich elements (AREs). AU-rich mRNAs are a subcategory of mRNAs that have AREs in their 3'-Untranslated Regions (UTRs). These ARE-genes have been observed to correlate with rapid mRNA decay patterns. They comprise approximately 12% of all transcripts and are known to encode for a group of proteins that have involvement in the inflammatory response. Trans-acting regulatory mechanisms are micro RNAs (miRNAs) in eukaryotes, and small RNAs (sRNA) in prokaryotes. Misregulation of these mechanisms can lead to many disease states if rapid mRNA decay does not occur, leading to tumorigenesis, and eventually, different types of cancer. In this project, the TNF-α ARE was studied in both serum-positive and quiescent G0 conditions in order to analyze whether the translation of the gene differed in any respect due to the binding of a known miRNA called miR-130a. Additionally, both serum-positive and one-day serum-starved quiescent G0 conditions were analyzed for eIF5B and FXR1 levels to analyze whether there was a correlation between the two proteins.

Cardiac muscle function necessitates the meticulous assembly and interactions of several cytoskeletal and regulatory proteins into specialized structures that orchestrate contraction and transmission forces. Despite extensive studies identifying the protein components responsible for these important aspects of heart development, putative RNA based mechanisms remain poorly understood, even with their demonstrated importance in other tissues. Evidence suggests that post-transcriptional regulation is critical for muscle function, but the molecular players involved (RNA binding proteins and mRNA targets) have remained elusive. We investigated the molecular mechanisms and targets of the muscle-specific Fragile X Related protein-1 (FXR1), an RNA binding protein whose absence leads to perinatal lethality in mice. Loss of FXR1 results in global protein level alterations. Morphological and biochemical analyses of Fxr1^(-/-) mice revealed severe disruption of intercalated disc and costamere architecture and composition. We identified several candidate mRNAs specifically enriched in the FXR1 protein complex. Two targets that likely contribute to the architectural defects are desmoplakin (dsp) and talin2 (tln2). In vitro assays indicate that FXR1 binds to these mRNA targets directly and represses their translation. Additionally, we provide preliminary evidence that the Fxr1^(-/-) mice mimic a hypothyroid state of cardiac gene expression, with alterations in myosin heavy chain and troponin I isoforms. Our findings reveal the first mRNA targets of FXR1 in muscle and support translational repression as a novel mechanism for cardiac muscle development and function.

The Fragile X-related mental retardation 1 (FXR1) is an N6-Methyladenosine reader involved in mRNAs metabolism like mRNA splicing, stability, transport, and miRNA regulation. It is also important in transcription, cell proliferation, differentiation, translation, polysome assembly and stress granule assembly. The protein is present in all eukaryotic cells, but so far it has been specifically essential for correct neural function. Until now, FXR1 has not been investigated in the concept of Human Adenovirus infection but we have observed an upregulation of FXR1 during the late phase of the Human Adenovirus 5 (HAdV-5) infection and an upregulation of some late HAdV-5 proteins in HeLa cells overexpressing FXR1. Our results furthermore showed that a FXR1 knockdown resulted in a reduced level of some HAdV-5 proteins at the same time as HAdV-5 mRNA were stabilized, indicating that FXR1 might be involved in translation of HAdV-5 late genes. Further investigation of the mechanism behind FXR1 mediated translation, a Death-associated protein 5 (DAP5) was founded to have an overall effect on the translation of HAdV-5 late proteins. / Part of a post-doctoral research