title: L1 elements, processed pseudogenes and retrogenes in mammalian genomes.
abstract: Long interspersed nuclear elements 1 (L1 elements or LINE1) are the most active autonomous retrotransposons in mammalian genomes. In addition to L1 elements themselves, other protein-coding mRNAs can also be reverse transcribed and integrated into the genome through the L1-mediated retrotransposition, leading to the formation of processed pseudogenes (PPs) and retrogenes, both of which are characterized by the lack of introns and the presence of a 3' polyA tract and flanking direct repeats. PPs are unable to encode a functional protein and have accumulated frameshift mutations and premature stop codons during evolution. A few of PPs are transcriptionally active. Retrogenes preserve undisrupted coding frames and are capable of encoding a functional protein that is identical or nearly identical to that of the progenitor gene. There is a significant excess of retrogenes that originate from the X chromosome and are retrotransposed into autosomes, and most of these retrogenes are specially expressed in male germ cells, suggesting the inactivation of X-linked genes during male meiosis provides a strong selection pressure on retrogenes originating from the X chromosome.
authors.affiliation: Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian, China.
authors.forename: Wenyong
authors.initials: W
authors.lastname: Ding
authors.forename: Lin
authors.initials: L
authors.lastname: Lin
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
authors.forename: Jianwu
authors.initials: J
authors.lastname: Dai
mesh_terms: D000818:Animals; D016678:Genome / Q000235:genetics*; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics*; D008322:Mammals / Q000235:genetics*; D011544:Pseudogenes / Q000235:genetics*; D018626:Retroelements / Q000235:genetics*
chemical_list: D018626:Retroelements