Joined: May 2002
Birth of two chimeric genes in the Hominidae lineage.
Courseaux A, Nahon JL.
Science 2001 Feb 16;291(5507):1293-7
PubMed, Full text (May require subscription)
|How genes with newly characterized functions originate remains a fundamental question. PMCHL1 and PMCHL2, two chimeric genes derived from the melanin-concentrating hormone (MCH) gene, offer an opportunity to examine such an issue in the human lineage. Detailed structural, expression, and phylogenetic analysis showed that the PMCHL1 gene was created near 25 million years ago (Ma) by a complex mechanism of exon shuffling through retrotransposition of an antisense MCH messenger RNA coupled to de novo creation of splice sites. PMCHL2 arose 5 to 10 Ma by an event of duplication involving a large chromosomal region encompassing the PMCHL1 locus. The RNA expression patterns of those chimeric genes suggest that they have been submitted to strong regulatory constraints during primate evolution.|
Here is the proposed model for the evolution of these genes (B):
|(B) Proposed model for the emergence of MCH-derived sequence onto chromosome 5p. (a) An AROM mRNA initiating in the CS3-5 region and ending at poly A (b) polyadenylation site was retrotransposed onto the equivalent of chromosome 5p at the time of Catarrhini divergence 25 to 30 Ma. (b) After this first event or concurrent to it, an Alu sequence was inserted in intron A and a fragment corresponding to the 3' end of the retrotransposed mRNA (part of exon II-intron A-Alu) was broken and transposed to the downstream insertion site. This led to the PMCHL gene versions observed in Cercopithecoidea and Hominoidea. |
Edited by theyeti on Dec. 10 2002,23:33