Characterization of arrangement and expression of the beta-2 microglobulin locus in the sandbar and nurse shark.
ABSTRACT Beta 2 microglobulin (beta2m) is an essential subunit of major histocompatibility complex (MHC) type I molecules. In this report, beta2m cDNAs were identified and sequenced from sandbar shark spleen cDNA library. Sandbar shark beta2m gene encodes one amino acid less than most teleost beta2m genes, and 3 amino acids less than mammal beta2m genes. Although sandbar shark beta2m protein contains one beta sheet less than that of human in the predicted protein structure, the overall structure of beta2m proteins is conserved during evolution. Germline gene for the beta2m in sandbar and nurse shark is present as a single locus. It contains three exons and two introns. CpG sites are evenly distributed in the shark beta2m loci. Several DNA repeat elements were also identified in the shark beta2m loci. Sequence analysis suggests that the beta2m locus is not linked to the MHC I loci in the shark genome.
- Proceedings of The National Academy of Sciences - PNAS. 01/1993; 90(21):9882-9886.
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ABSTRACT: While the significance of middle repetitive elements had been neglected for a long time, there are again tendencies to ascribe most members of a given middle repetitive sequence family a functional role--as if the discussion of SINE (short interspersed repetitive elements) function only can occupy extreme positions. In this article, I argue that differences between the various classes of retrosequences concern mainly their copy numbers. Consequently, the function of SINEs should be viewed as pragmatic such as, for example, mRNA-derived retrosequences, without underestimating the impact of retroposition for generation of novel protein coding genes or parts thereof (exon shuffling by retroposition) and in particular of SINEs (and retroelements) in modulating genes and their expression. Rapid genomic change by accumulating retrosequences may even facilitate speciation [McDonald, J.F., 1995. Transposable elements: possible catalysts of organismic evolution. Trends Ecol. Evol. 10, 123-126.] In addition to providing mobile regulatory elements, small RNA-derived retrosequences including SINEs can, in analogy to mRNA-derived retrosequences, also give rise to novel small RNA genes. Perhaps not representative for all SINE/master gene relationships, we gained significant knowledge by studying the small neuronal non-messenger RNAs, namely BC1 RNA in rodents and BC200 RNA in primates. BC1 is the first identified master gene generating a subclass of ID repetitive elements, and BC200 is the only known Alu element (monomeric) that was exapted as a novel small RNA encoding gene.Gene 10/1999; 238(1):115-34. · 2.20 Impact Factor
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ABSTRACT: Current evidence on the long-term evolutionary effect of insertion of sequence elements is reviewed. There are three criteria for inclusion of an example: (i) the element was inserted far in the past and thus the event is not a transient mutation; (ii) the element is a member of a large group of similar sequences; (iii) the element now serves a useful function. There are 21 examples from Drosophila, sea urchin, human and mouse genomes that meet these criteria. Taken together, these examples show that the insertion of sequence elements in the genome has been a significant source of regulatory variation in evolution.Gene 01/1998; 205(1-2):177-82. · 2.20 Impact Factor