J1-crystallins of the cubomedusan jellyfish lens constitute a novel family encoded in at least three intronless genes.
The transparent cellular eye lens of the jellyfish (Tripedalia cystophora) contains three major proteins called J1-, J2-, and J3-crystallins. Here we have isolated cDNAs encoding three novel 37-kDa J1-crystallin polypeptides (J1A, J1B, and J1C) sharing 84-98% identity in amino acid sequence among themselves. Each polypeptide is encoded in a separate gene lacking introns. In contrast to the striking similarity of the coding regions, the 5'- and 3'-untranslated sequences of the three J1-crystallin mRNAs are completely different, consistent with an ancient duplication of their genes. Thermostability experiments showed that J1-crystallins remain soluble at 50 degrees C, but precipitate at 60 degrees C, suggesting that these major lens proteins are neither heat shock proteins nor unusually heat-resistant as are many vertebrate crystallins. Although J1 mRNAs appear polyadenylated, no typical polyadenylation signal was detected in the cDNAs. Surprisingly, the only obvious similarities among the 5'-flanking regions of the three J1-crystallin genes are putative TATA boxes and several CAAT sequences, consistent with fewer evolutionary constraints on the regulatory sequences than on the coding sequences of these crystallin genes.
Piatigorsky
J
J
Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892.
Horwitz
J
J
Norman
B L
BL
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D003459:Crystallins / Q000737:chemistry / Q000235:genetics*; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D015698:Genomic Library; D007438:Introns; D007908:Lens, Crystalline / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009838:Oligodeoxyribonucleotides; D010446:Peptide Fragments / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015183:Restriction Mapping; D037401:Scyphozoa / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
D003459:Crystallins; D009838:Oligodeoxyribonucleotides; D010446:Peptide Fragments; D012333:RNA, Messenger; D004247:DNA