Establishment and maintenance of transposon silencing in the male germ line
04/09/2012 - Room M203 at 14:00 - Pink Seminar
Transposable elements are mobile genetic elements that constitute a large fraction of mammalian genomes. In mammals, these highly mutagenic elements are epigenetically silenced throughout most of life to avoid the deleterious effects of transposition. Transposon silencing is erased and reestablished during germ cell reprogramming. This epigenetic process of transposon silencing is of fundamental importance for germ cell development and the genomic integrity of the gametes and thus the future soma. Highly conserved ribonuclear particles have evolved that target transposons for DNA methylation and subsequent epigenetic silencing. In the male germ line members of the Piwi subclade of the Argonaute family of proteins, Mili and Miwi2 are essential for de novo DNA methylation of transposons and spermatogenesis. Both Mili and Miwi2 bind a class of small non-coding RNAs known as Piwi-interacting RNAs (piRNAs) that are believed to act as guides for targeting of the respective RNPs. The Argonaute family is primarily defined by the presence of the Piwi domain that adopts a classical RNase H fold with some Argonaute proteins being active small-RNA guided endonucleases. The contribution and mechanism of the piRNA pathway to the establishment and maintenance of transposon silencing will be presented.