Studies on Silencing

发育遗传学部分主要对粟酒裂殖酵母中基因沉默和交配型转换的遗传学和分子生物学感兴趣。pombe）。在这种酵母中，交配型区域由3个位点组成：mat 1，mat 2和mat 3。mat 2和mat 3基因座总是沉默的，只作为转换转录活性mat 1基因座所需的遗传信息的供体。研究沉默。以前，我们发现沉默机制涉及染色体遗传的表观遗传改变，推测与垫区域相关的染色质。在分裂酵母中，标记交配型（mat 2/3）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。我们已经表明，一个含有染色体结构域的swi 6蛋白是一个剂量关键的组成部分，参与印迹的垫轨迹。印记的建立和维持与有丝分裂和减数分裂期间mat 2/3区域swi 6的募集和持续存在密切相关。值得注意的是，swi 6p在整个细胞中仍然与mat 2/3间隔结合，并且本身似乎是印记的一个组成部分。我们的分析表明，在mat 2/3位点的遗传单位包括DNA加上相关的swi 6蛋白复合物。有趣的是，沉默结构域被1.2KB反向重复序列包围，该序列阻止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导致沉默跨越这些异染色质屏障扩散。异染色质跨越屏障的扩散需要功能性Atf 1/Pcr 1、ATF-CREB家族蛋白，而不是先前参与沉默的RNA干扰Dcr 1、Ago 1或Rdp 1因子。我们的工作继续定义沉默的遗传决定因素，并直接影响解释真核细胞分化和癌症的发展，作为表观遗传控制的破坏，构成了不必要的细胞生长的一个突出机制。

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.