Sidorova J, Breeden L
Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
Genetics. 1999 Jan;151(1):45-55. doi: 10.1093/genetics/151.1.45.
Ankyrin (ANK) repeats were first found in the Swi6 transcription factor of Saccharomyces cerevisiae and since then were identified in many proteins of eukaryotes and prokaryotes. These repeats are thought to serve as protein association domains. In Swi6, ANK repeats affect DNA binding of both the Swi4/Swi6 and Mbp1/Swi6 complexes. We have previously described generation of random mutations within the ANK repeats of Swi6 that render the protein temperature sensitive in its ability to activate HO transcription. Two of these SWI6 mutants were used in a screen for high copy suppressors of this phenotype. We found that MSN1, which encodes a transcriptional activator, and NHP6A, which encodes an HMG-like protein, are able to suppress defective Swi6 function. Both of these gene products are involved in HO transcription, and Nhp6A may also be involved in CLN1 transcription. Moreover, because overexpression of NHP6A can suppress caffeine sensitivity of one of the SWI6 ANK mutants, swi6-405, other SWI6-dependent genes may also be affected by Nhp6A. We hypothesize that Nhp6A and Msn1 modulate Swi6-dependent gene transcription indirectly, through effects on chromatin structure or other transcription factors, because we have not been able to demonstrate that either Msn1 or Nhp6A interact with the Swi4/Swi6 complex.
锚蛋白（ANK）重复序列最初在酿酒酵母的Swi6转录因子中被发现，自那时起在真核生物和原核生物的许多蛋白质中都有鉴定。这些重复序列被认为是蛋白质结合结构域。在Swi6中，ANK重复序列影响Swi4/Swi6和Mbp1/Swi6复合物的DNA结合。我们之前描述了在Swi6的ANK重复序列内产生随机突变，使该蛋白在激活HO转录的能力上对温度敏感。其中两个SWI6突变体用于筛选这种表型的高拷贝抑制子。我们发现，编码转录激活因子的MSN1和编码类HMG蛋白的NHP6A能够抑制有缺陷的Swi6功能。这两种基因产物都参与HO转录，并且Nhp6A可能也参与CLN1转录。此外，由于NHP6A的过表达可以抑制SWI6 ANK突变体之一swi6 - 405的咖啡因敏感性，其他依赖Swi6的基因可能也受Nhp6A影响。我们推测Nhp6A和Msn1通过对染色质结构或其他转录因子的影响间接调节依赖Swi6的基因转录，因为我们未能证明Msn1或Nhp6A与Swi4/Swi6复合物相互作用。
