Volume 272, Number 18,
Issue of May 2, 1997
pp. 12076-12082
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.
Transfection Analysis of Expression of mRNA Isoforms Encoding
the Nuclear Autoantigen La/SS-B
(Received for publication, November 18, 1996)
Daniel
Grölz
,
Julia
Laubinger
,
Friederike
Wilmer
,
Helmut
Tröster
and
Michael
Bachmann
From the Institut für Physiologische Chemie,
Johannes-Gutenberg Universität, Duesbergweg 6, D-55099 Mainz Germany
Transcription of the gene encoding for the
nuclear autoantigen La resulted in La mRNA isoforms. A promoter
switching combined with an alternative splicing pathway replaced the
exon 1 with the exon 1
. The exon 1 contained GC-rich regions and an
oligo(U) tail of 23 uridine residues. Moreover, it encoded for three
open reading frames upstream of the La protein reading frame. Despite this unusual structure, when exon 1 La mRNAs were expressed in transfected cells, both exon 1 and 1 La mRNAs were translated to
La protein, whereas the upstream open reading frames of the exon 1
were not translated. In addition to full-length exon 1 La mRNAs
5-shortened exon 1 La mRNAs were detected. The exon 1 5-starts
varied in dependence on the analyzed tissues. Like the full-length exon
1 La mRNA a 5-shortened exon 1 construct starting downstream of
the oligo(U) tail but upstream of the open reading frames 2 and 3 was
also well translated when transfected in mouse cells. Thus all La
mRNA forms represent functional La mRNAs.
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