Graïa F, Lespinet O, Rimbault B, Dequard-Chablat M, Coppin E, Picard M
Institut de Génétique et Microbiologie, UMR-CNRS 8621, Batiment 400, Université Paris-Sud, 91405 Orsay cedex, France.
Mol Microbiol. 2001 May;40(3):586-95. doi: 10.1046/j.1365-2958.2001.02367.x.
RIP (repeat-induced point mutation) is a silencing process discovered in Neurospora crassa and so far clearly established only in this species as a currently occurring process. RIP acts premeiotically on duplicated sequences, resulting in C-G to T-A mutations, with a striking preference for CpA/TpG dinucleotides. In Podospora anserina, an RIP-like event was observed after several rounds of sexual reproduction in a strain with a 40 kb tandem duplication resulting from homologous integration of a cosmid in the mating-type region. The 9 kb sequenced show 106 C-G to T-A transitions, with 80% of the replaced cytosines located in CpA dinucleotides. This led to the alteration of at least six genes, two of which were unidentified. This RIP-like event extended to single-copy genes between the two members of the repeat. The overall data show that the silencing process is strikingly similar to a light form of RIP, unaccompanied by C-methylation. Interestingly, the N. crassa zeta-eta sequence, which acts as a potent de novo C-methylation RIP signal in this species, is weakly methylated when introduced into P. anserina. These results demonstrate that RIP, at least in light forms, can occur beyond N. crassa.
重复诱导点突变（RIP）是在粗糙脉孢菌中发现的一种沉默过程，迄今为止，仅在该物种中明确证实这是一种当前正在发生的过程。RIP在减数分裂前作用于重复序列，导致C-G到T-A的突变，对CpA/TpG二核苷酸有明显偏好。在嗜热栖热放线菌中，在一个菌株经过几轮有性繁殖后观察到类似RIP的事件，该菌株因黏粒在交配型区域的同源整合而产生了一个40 kb的串联重复。测序的9 kb片段显示有106个C-G到T-A的转换，其中80%被取代的胞嘧啶位于CpA二核苷酸中。这导致至少六个基因发生改变，其中两个基因尚未鉴定。这种类似RIP的事件扩展到了重复序列两个成员之间的单拷贝基因。总体数据表明，这种沉默过程与轻度形式的RIP非常相似，且不伴有C-甲基化。有趣的是，粗糙脉孢菌的zeta-eta序列在该物种中作为一种强大的从头C-甲基化RIP信号，当被引入嗜热栖热放线菌时，甲基化程度较弱。这些结果表明，至少轻度形式的RIP可以在粗糙脉孢菌之外发生。
