Comments |
piRNAs (Piwi-interacting RNAs) have been gaining increasing attention because of their role in protecting the germline genome. Their existence has been demonstrated in the testes and ovaries of zebrafish and Drosophila, as well as in the testes of mammals. piRNAs are ~24–30 nt-long they have a 5' uridine bias and a 2'-O-methylated 3'-end. About 17% of mammalian piRNAs map to repeat sequences, including LINEs, SINEs, and several classes of DNA transposons [4], and nearly one million piRNA molecules have been reported per spermatocyte or round spermatid [5]. The major sources of piRNAs are discrete heterochromatic piRNA clusters characterized by nested, fragmented and immobilized transposon remnants [6]. piRNAs are associated with Piwi proteins. [Digits in parentheses refer to literature cited in article] |