PMC:4502370 / 25185-26687 JSONTXT

{"project":"2_test","denotations":[{"id":"25911228-15340060-43354270","span":{"begin":546,"end":550},"obj":"15340060"}],"text":"The identification of two RNA polymerase subunits as dosage suppressors of tgs1∆ suggested a novel connection between TMG caps and transcription. The connection via Rpo31 to RNA polymerase III, which is responsible for the synthesis of many essential noncoding RNAs (5S rRNA, U6 snRNA, tRNAs), was particularly puzzling insofar as none of the known Pol III transcripts have 5′ TMG (or m7G) caps. One scenario that might explain the genetic suppressor results is that the loss of TMG caps affects nucleolar architecture and function (Colau et al. 2004) such that the assembly or activity of Pol III is compromised at cold temperature, and this defect can be overcome, in part, by overexpressing either RPO31 or RPO26. If this is the case, then we might expect that simultaneously overexpressing RPO31 and RPO26 would afford better growth of tgs1∆ cells at 18° than increasing the gene dosage of either gene alone. We tested this by introducing RPO31 and RPO26 on the same 2-µ plasmid, but observed no better rescue of tgs1∆ growth in the cold than that afforded by 2-µ RPO26 (data not shown). Another prediction of the above scenario is that tgs1∆ suppression should require high gene dosage. To address this issue, we placed the RPO31 and RPO26 genes on CEN plasmids and transformed them into tgs1∆ cells. The striking finding was that provision of RPO26 or RPO31 on a CEN plasmid was just as effective as the 2-µ RPO26 or RPO31 plasmids in restoring tgs1∆ growth at restrictive temperature (Figure 4)."}