Di Como C J, Bose R, Arndt K T
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724-2212.
Genetics. 1995 Jan;139(1):95-107. doi: 10.1093/genetics/139.1.95.
The Saccharomyces cerevisiae SIS2 gene was identified by its ability, when present on a high copy number plasmid, to increase dramatically the growth rate of sit4 mutants. SIT4 encodes a type 2A-related protein phosphatase that is required in late G1 for normal G1 cyclin expression and for bud initiation. Overexpression of SIS2, which contains an extremely acidic carboxyl terminal region, stimulated the rate of CLN1, CLN2, SWI4 and CLB5 expression in sit4 mutants. Also, overexpression of SIS2 in a CLN1 cln2 cln3 strain stimulated the growth rate and the rate of CLN1 and CLB5 RNA accumulation during late G1. The SIS2 protein fractionated with nuclei and was released from the nuclear fraction by treatment with either DNase I or micrococcal nuclease, but not by RNase A. This result, combined with the finding that overexpression of SIS2 is extremely to a strain containing lower than normal levels of histones H2A and H2B, suggests that SIS2 might function to stimulate transcription via an interaction with chromatin.
酿酒酵母SIS2基因是通过其在高拷贝数质粒上时能够显著提高sit4突变体生长速率的能力而被鉴定出来的。SIT4编码一种2A型相关蛋白磷酸酶，在G1晚期，它对于正常的G1细胞周期蛋白表达和芽起始是必需的。SIS2含有一个极端酸性的羧基末端区域，其过表达刺激了sit4突变体中CLN1、CLN2、SWI4和CLB5的表达速率。此外，在CLN1 cln2 cln3菌株中过表达SIS2刺激了生长速率以及G1晚期CLN1和CLB5 RNA的积累速率。SIS2蛋白与细胞核一起分级分离，通过用DNase I或微球菌核酸酶处理可从核级分中释放出来，但用RNase A处理则不能。这一结果，再加上SIS2过表达对组蛋白H2A和H2B水平低于正常的菌株极为敏感这一发现，表明SIS2可能通过与染色质相互作用来发挥刺激转录的功能。
