X chromosome inactivation and Xist evolution in a rodent lacking LINE-1 activity.
Dosage compensation in eutherian mammals occurs by inactivation of one X chromosome in females. Silencing of that X chromosome is initiated by Xist, a large non-coding RNA, whose coating of the chromosome extends in cis from the X inactivation center. LINE-1 (L1) retrotransposons have been implicated as possible players for propagation of the Xist signal, but it has remained unclear whether they are essential components. We previously identified a group of South American rodents in which L1 retrotransposition ceased over 8 million years ago and have now determined that at least one species of these rodents, Oryzomys palustris, still retains X inactivation. We have also isolated and analyzed the majority of the Xist RNA from O. palustris and a sister species retaining L1 activity, Sigmodon hispidus, to determine if evolution in these sequences has left signatures that might suggest a critical role for L1 elements in Xist function. Comparison of rates of Xist evolution in the two species fails to support L1 involvement, although other explanations are possible. Similarly, comparison of known repeats and potential RNA secondary structures reveals no major differences with the exception of a new repeat in O. palustris that has potential to form new secondary structures.
Cantrell
Michael A
MA
Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America.
Carstens
Bryan C
BC
Wichman
Holly A
HA
D000818:Animals; D001483:Base Sequence; D018899:CpG Islands; D004247:DNA / Q000235:genetics; D019175:DNA Methylation; D019143:Evolution, Molecular; D005260:Female; D020084:Long Interspersed Nucleotide Elements; D008969:Molecular Sequence Data; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D016205:Sigmodontinae / Q000235:genetics*; D013045:Species Specificity; D049951:X Chromosome Inactivation
D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C077885:XIST non-coding RNA; D004247:DNA