Volume 271, Number 28,
Issue of July 12, 1996
pp. 16945-16951
©1996 by The American Society for Biochemistry and Molecular Biology, Inc.
Extensive Alternative Splicing within the Amino-propeptide Coding
Domain of
2(XI) Procollagen mRNAs
EXPRESSION OF TRANSCRIPTS ENCODING TRUNCATED PRO-
CHAINS
(Received for publication, July 13, 1995, and in revised form, March 14, 1996)
Vincent C. H.
Lui
,
Ling Jim
Ng
,
Eric W. Y.
Sat
,
John
Nicholls
¶
and
Kathryn S. E.
Cheah
From the Departments of Biochemistry and
¶ Pathology, The University of Hong Kong, 5 Sassoon
Road, Hong Kong
Heterogeneity in type XI procollagen structure is
extensive because all three
(XI) collagen genes undergo complex
alternative splicing within the amino-propeptide coding domain. Exon 7 of the human and exons 6-8 of the mouse
2(XI) collagen genes,
encoding part of the amino-propeptide variable region, have recently
been shown to be alternatively spliced. We show that exon 6-containing
mRNAs for human
2(XI) procollagen are expressed at 28 weeks in
fetal tendon and cartilage but not at 38-44 days or 11 weeks. In the
mouse, exon 6 is expressed in chondrocytes from 13.5 days onward. We
recently identified conserved sequences within intron 6 of the human
and mouse
2(XI) collagen genes, containing additional consensus
splice acceptor and donor sites that potentially increase the size of
exon 7, dividing it into three parts, designated 7A, 7B, and 7C. We
show by reverse transcription polymerase chain reaction and in
situ hybridization that these potential splice sites are used to
yield additional
2(XI) procollagen mRNA splice variants that are
expressed in fetal tissues. In human, expression of exon 7B-containing
transcripts may be developmental stage-specific. Interestingly,
inclusion of exon 7A or exon 7B in human and mouse
2(XI) procollagen
mRNAs, respectively, would result in the insertion of an in-frame
termination codon, suggesting that some of the additional splice
variants encode a truncated pro-
2(XI) chain.