THE CHICKEN CP49 GENE CONTAINS AN EXTRA EXON COMPARED TO THE HUMAN CP49 GENE WHICH IDENTIFIES AN IMPORTANT STEP IN THE EVOLUTION OF THE EYELENS INTERMEDIATE FILAMENT PROTEINS
P. Wallace et al., THE CHICKEN CP49 GENE CONTAINS AN EXTRA EXON COMPARED TO THE HUMAN CP49 GENE WHICH IDENTIFIES AN IMPORTANT STEP IN THE EVOLUTION OF THE EYELENS INTERMEDIATE FILAMENT PROTEINS, Gene, 211(1), 1998, pp. 19-27
The gene structure for chicken CP49 gene is presented. It differs from
the human CP49 gene with the presence of an extra exon in helix IB an
d the apparent loss of an intron, intron H. The CP49 gene localises to
chromosome 2 in the chicken genome where it is flanked by homologues
that map to human chromosome 10p13 (VIM) 6p24-p23 (BMP6). Two transcri
pts, CP49 and CP49ins, are produced from the single chicken CP49 gene.
The difference is a 49-amino-acid insertion in helix IB of CP49 that
is encoded by a novel exon found in the chicken CP49 gene. An extended
helix IB is believed to be a characteristic of the ancestral intermed
iate filament protein as it is found in many invertebrate intermediate
filament proteins but has been lost from all vertebrate intermediate
filament proteins except the nuclear lamins. Although the intron posit
ion and length of the helix IB insert sequences in CP49ins differ to t
hose found both in the invertebrate intermediate filament proteins and
the vertebrate lamins, the CP49 gene is the first vertebrate cytoplas
mic intermediate filament protein to be described with an extended hel
ix IB. The chicken CP49 gene is also the first where differential spli
cing can remove such a feature. Human and bovine CP49 appear to have l
ost the helix IB insert sequences, and so the avian CP49 gene provides
an interesting evolutionary link between the eye lens proteins and th
e ancestral intermediate filament protein. (C) 1998 Elsevier Science B
.V. All rights reserved.