It was shown, previously that N. crassa contains an endo-exonuclease which exist in two forms, an active form and an inactive form activated by trypsin treatment in vitro. Both of these forms were found in the cytosol and in mitochondria, but only the active form is present in the vacuoles. In the present work, it has been shown that both forms are also present in the nuclei bound to the chromatin. / Active endo-exonuclease was previously implicated in DNA repair and in this study additional evidence was obtained in further support of such a role: (i) the mutagen sensitive uvs-3 mutant of N. crassa was found to contain only 10% of the level of active enzyme in the two DNA-containing organelles, in comparison to the levels found in the wild-type, (ii) in response to low doses of the DNA-damaging agent 4-nitroquinoline 1-oxide (4-NQO), the inactive enzyme decrease and the active form increase in the DNA-containing organelles indicating that the inactive enzyme may have been converted proteolytically to the active form. This response did not occur in the uvs-3 mutant. / Under a different stress, namely heat shock, endo-exonuclease was regulated differently in the DNA-containing organelles. Active enzyme was released from the nuclei, mitochondria, and vacuoles into the cytosol where it was nearly completely inhibited by a specific inhibitor induced by heat shock. This heat shock-induced inhibitor shared some properties in common with a constitutive endo-exonuclease inhibitor recently isolated from this laboratory. However, there were also some distinct differences between these two inhibitors. At least one difference may be explained by phosphorylation of the heat shock inhibitor.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.74244 |
| Date | January 1989 |
| Creators | Ramotar, Dindial |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biochemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000936583, proquestno: AAINL57302, Theses scanned by UMI/ProQuest. |
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