An Investigation of the cis and trans Factors Required for Maintaining Adjacent Gene Co-regulation in Saccharomyces cerevisiae
<p>For a cell to be able to divide actively and progress through the cell cycle, a large number of new proteins are required. The production of proteins is carried out by ribosomes, whose biogenesis, in turn, plays an important role in the overall growth of the cell. Since ribosome production is an energetically demanding process, the cell has to ensure that it is precisely regulated in response to varying cellular conditions. Many ribosomal RNA (rRNA), ribosomal and rRNA biosynthesis (RRB) and ribosomal protein (RP) genes are essential in the production of ribosomes. The RRB regulon contains ~300 genes, and is distinct from the RP regulon, in that its members are required for the production of rRNA’s. A significant number of the genes in the RRB and RP regulon occur as immediately adjacent pairs in all possible orientations i.e. convergent, tandem and divergent. Studies in our lab have shown the significance of gene pairing in regulating gene expression, in particular for the RRB gene pair<em> MPP10-YJR003C</em>. The transcriptional regulation of <em>YJR003C</em> from the promoter of <em>MPP10</em> has also been experimentally studied. We show that AGC between <em>MPP10-YJR003C</em> could be abrogated by an active RNA Pol II transcriptional unit. Since the coding region of <em>YJR003C</em> has been shown not to play a role in maintaining AGC, it is possible that the 5’ and 3’ untranslated regions of <em>YJR003C</em> might play a role in maintaining AGC with <em>MPP10</em>. The requirement of the SAGA component Spt20 in maintaining AGC between <em>MPP10</em> and <em>YJR003C</em> is shown, hinting towards the importance of maintaining the structural integrity of the SAGA complex for AGC. The Sus1 subunit of the SAGA complex on the other hand is not required from maintaining the AGC in the RP gene pair (<em>RPS27A</em>-<em>RSM22</em>). AGC between <em>MPP10</em>-<em>YJR003C</em> could be partially dependent on the activity of Swi6, a chromatin remodeler. The phenomenon of AGC is not confined to the RRB regulon but is also seen in the RP regulon (<em>RPS27A</em>-<em>RSM22</em>), hinting towards the possibility of this being a widespread one within the genome.</p>