The human gene for gammaS-crystallin: alternative transcripts and expressed sequences from the first intron.
OBJECTIVE
gammaS-crystallins are major components of adult vertebrate lenses. Here we examine the population of gammaS transcripts in adult human lens and the structure of the human CRYGS genes.


METHODS
Adult lens human transcripts were obtained from NEIBANK, an Expressed Sequence Tag (EST) analysis of human eye tissues. The human CRYGS gene was isolated as a PAC clone and sequenced by direct and PCR-based methods.


RESULTS
As judged by EST frequency, gammaS is one of the most abundant transcripts in the adult human lens, ranking just behind betaB2-, alphaB- and alphaA-crystallins. EST analysis reveals two transcript sizes resulting from alternative AATAAA and ATTAAA polyadenylation signals. In addition, one cDNA clone was found to contain a novel insert sequence that disrupted the open reading frame. Gene sequencing confirmed that this insert comes from intron 1 and is part of a sequence corresponding to a cluster of unidentified human transcripts in dbEST. Human and mouse gammaS gene proximal promoter sequences were compared and showed a high degree of evolutionary conservation, including consensus binding sites for transcription factors of the maf and SOX families.


CONCLUSIONS
The human CRYGS gene can give rise to at least two transcripts through alternative polyadenylation. A minor transcript results from alternative splicing into sequences in intron 1. These sequences form part of a transcription unit (Mys) expressed in several non-lens tissues. The identity and function Mys of is not yet known, however, the cryptic splicing of CRYGS could produce a defective protein product, with potentially deleterious results for the adult human lens.
Wistow
G
G
Section on Molecular Structure and Function, National Eye Institute, National Institutes of Health, Bethesda, MD 20892-2740, USA. graeme@helix.nih.gov
Sardarian
L
L
Gan
W
W
Wyatt
M K
MK
D000328:Adult; D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003459:Crystallins / Q000235:genetics*; D020224:Expressed Sequence Tags; D005786:Gene Expression Regulation; D006801:Humans; D007438:Introns; D051379:Mice; D008969:Molecular Sequence Data; D011061:Poly A / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
D003459:Crystallins; D012333:RNA, Messenger; D011061:Poly A