Jiang Y W, Stillman D J
Department of Cellular, Viral, and Molecular Biology, University of Utah Medical Center, Salt Lake City 84132, USA.
Genetics. 1995 May;140(1):103-14. doi: 10.1093/genetics/140.1.103.
The yeast SIN4 gene functions in the transcriptional activation and repression of diverse yeast genes. Previous experiments suggest a sin4 mutation affects chromatin structure and thus alters transcriptional regulation. In this report we show that SIN4 is required for full expression of the HIS4, Ty1, and MAT alpha genes, in addition to the previously described SIN4-dependence of CTS1 expression. All of these genes contain within their promoters a binding site for the Rap1p transcriptional regulator. However, SIN4 does not play a direct role either in transcriptional activation or repression by Rap1p. The HIS4 gene can be activated by either of two pathways, the basal or the inducible pathway, and experiments are described that show that a sin4 mutation affects both pathways. It was shown previously that mutation of the Rap1p binding site in the HIS4 promoter causes a similar effect on HIS4 expression and that this promoter mutation also causes a change in chromatin structure. The SNF2/SWI2 gene is also required for full HIS4 expression, and we show that a sin4 snf2 double mutant is not synergistic compared to either single mutant. We show that nucleosomes are positioned at the HIS4 promoter and that this positioning is disrupted in a snf2 mutant but not in a sin4 mutant. These findings suggest that SIN4 plays a distinct role in transcriptional regulation.
酵母SIN4基因在多种酵母基因的转录激活和抑制中发挥作用。先前的实验表明，sin4突变会影响染色质结构，从而改变转录调控。在本报告中，我们表明，除了先前描述的CTS1表达对SIN4的依赖性外，HIS4、Ty1和MATα基因的充分表达也需要SIN4。所有这些基因在其启动子内都含有Rap1p转录调节因子的结合位点。然而，SIN4在Rap1p介导的转录激活或抑制中均不发挥直接作用。HIS4基因可通过基础途径或诱导途径中的任何一条被激活，本文描述的实验表明，sin4突变会影响这两条途径。先前有研究表明，HIS4启动子中Rap1p结合位点的突变对HIS4表达有类似影响，且该启动子突变也会导致染色质结构的改变。SNF2/SWI2基因对于HIS4的充分表达也是必需的，我们发现，与单突变体相比，sin4 snf2双突变体没有协同作用。我们发现核小体定位于HIS4启动子处，且这种定位在snf2突变体中被破坏，但在sin4突变体中未被破坏。这些发现表明，SIN4在转录调控中发挥着独特的作用。
