Studies on Silencing

发育遗传学部分主要研究裂殖酵母(S.pombe)基因沉默和交配型转换的遗传学和分子生物学。在该酵母中，交配型区域由3个基因座组成：mat1、mat2和mat3。Mat2和mat3基因座总是沉默的，只作为基因信息的供体，这是转换转录活性的mat1基因座所需的。关于沉默的研究。以前，我们发现沉默机制涉及染色体可遗传的表观遗传学改变，推测是与MAT区域相关的染色质改变。在分裂酵母中，标记交配型(mat2/3)区域的表观遗传印记有助于沉默状态的遗传，但这种印记的性质尚不清楚。我们已经证明，含有色域的SWI6蛋白是印记MAT基因的剂量关键成分。印迹的建立和维持与有丝分裂和减数分裂过程中sw6在mat2/3区域的招募和持续密切相关。值得注意的是，wi6p仍然与整个细胞的mat2/3区间结合，它本身似乎是印记的一个组成部分。我们的分析表明，mat2/3基因座的遗传单位由DNA加上相关的sw6蛋白复合体组成。有趣的是，沉默的区域被1.2kb的反向重复序列所包围，这些反向重复序列阻止了异染色质扩散到染色体的相邻区域。我们已经发现，脱氧核糖核苷酸生物合成中的突变会导致沉默跨越这些异染色质障碍传播。异染色质的跨屏障扩散需要具有功能的atf1/PCR1、ATF-CREB家族蛋白，而不是以前被认为与沉默有关的RNA干扰Dcr1、Ago1或Rdp1因子。我们的工作继续定义沉默的遗传决定因素，并对解释真核细胞分化和癌症发展为破坏表观遗传控制，构成不想要的细胞生长的显著机制具有直接意义。

The Developmental Genetics Section is mainly interested in the genetics and molecular biology of gene silencing and mating-type switching in Schizosaccharomyces pombe (s. pombe). In this yeast, the mating-type region consists of 3 loci: mat1, mat2, and mat3. The mat2 and mat3 loci are always silent and only act as donors of the genetic information that is required for switching the transcriptionally active mat1 locus. Studies on Silencing. Previously, we found that the silencing mechanism involves a chromosomally heritable epigenetic alteration, presumably of chromatin associated with the mat region. In fission yeast, an epigenetic imprint marking the mating-type (mat2/3) region contributes to inheritance of the silenced state, but the nature of this imprint is unknown. We have shown that a chromodomain-containing swi6 protein is a dosage-critical component involved in imprinting the mat locus. The establishment and maintenance of the imprint are tightly coupled to the recruitment and persistence of swi6 at the mat2/3 region during mitosis as well as meiosis. Remarkably, swi6p remains bound to the mat2/3 interval throughout the cell and itself seems to be a component of the imprint. Our analyses suggest that the unit of inheritance at the mat2/3 locus comprises the DNA plus the associated swi6 protein complex. Interestingly, the silenced domain is bracketed by 1.2KB inverted repeat sequences that block spreading of heterochromatin to adjoining regions of chromosome. We have discovered that mutations in deoxyribonucleotide biosynthesis cause spreading of silencing across these heterochromatin barriers. The spreading of heterochromatin across barriers requires functional Atf1/Pcr1, ATF-CREB family proteins, but not the RNA-interference Dcr1, Ago1, or Rdp1 factors that were previously implicated in silencing. Our work continues to define the genetic determinants of silencing and has direct implications for explaining eukaryotic cellular differentiation and cancer development as a disruption of epigenetic controls, constituting a prominent mechanism of unwanted cellular growth.