Lorentz A, Ostermann K, Fleck O, Schmidt H
Institut für Genetik, Technische Universität Braunschweig, Germany.
Gene. 1994 May 27;143(1):139-43. doi: 10.1016/0378-1119(94)90619-x.
The switching gene swi6 of Schizosaccharomyces pombe is involved in the repression of the silent mating-type loci mat2 and mat3. We have cloned the gene by functional complementation of the switching defect of the swi6-115 mutation. DNA sequence analyses revealed an open reading frame of 984 bp coding for a putative protein of 328 amino acids (aa). The isolation of a swi6 cDNA confirmed this result. Gene replacement showed that swi6 is not essential for viability. The Swi6 protein is very hydrophilic; it contains 41% charged aa. A region of 48 aa is homologous to a sequence motif found in the chromatin-associated proteins, HP1 and Polycomb (Drosophila melanogaster), M31, M32 and M33 (mouse), and the human HSM1 protein. This motif is called chromo domain (chromatin organization modifier). Our results indicate that Swi6 is a structural component of chromatin. Swi6 may have the function to compact mat2 and mat3 into a heterochromatin-like conformation which represses the transcription of these silent cassettes.
粟酒裂殖酵母的转换基因swi6参与沉默交配型基因座mat2和mat3的抑制作用。我们通过对swi6 - 115突变体的转换缺陷进行功能互补克隆了该基因。DNA序列分析揭示了一个984 bp的开放阅读框，编码一个由328个氨基酸（aa）组成的推定蛋白质。swi6 cDNA的分离证实了这一结果。基因替换表明swi6对于细胞生存力并非必需。Swi6蛋白具有很强的亲水性；它含有41%的带电荷氨基酸。一个由48个氨基酸组成的区域与在染色质相关蛋白HP1和多梳蛋白（果蝇）、M31、M32和M33（小鼠）以及人类HSM1蛋白中发现的一个序列基序同源。这个基序被称为染色体结构域（染色质组织修饰因子）。我们的结果表明Swi6是染色质的一个结构成分。Swi6可能具有将mat2和mat3压缩成类似异染色质构象的功能，从而抑制这些沉默基因盒的转录。
