NOVEL HETEROGENEITY EXISTS IN THE 5'-UNTRANSLATED REGION OF THE BETA-GALACTOSIDE ALPHA-2,6-SIALYLTRANSFERASE MESSENGER-RNAS IN THE HUMAN B-LYMPHOBLASTOID CELL-LINE, LOUCKES
Nw. Lo et Jty. Lau, NOVEL HETEROGENEITY EXISTS IN THE 5'-UNTRANSLATED REGION OF THE BETA-GALACTOSIDE ALPHA-2,6-SIALYLTRANSFERASE MESSENGER-RNAS IN THE HUMAN B-LYMPHOBLASTOID CELL-LINE, LOUCKES, Biochemical and biophysical research communications, 228(2), 1996, pp. 380-385
Multiple mRNA isoforms are generated from SIAT1, the gene encoding the
beta-galactoside alpha 2,6-sialyltransferase (ST6Gal I, SiaT-1, ST6N,
alpha 2,6ST). These isoforms are transcriptionally initiated from a n
umber of physically distinct promoter regions. In human B-lymphocytic
cells, two SIAT1 mRNA isoforms have been identified. In order to deter
mine if additional SIAT1 mRNA isotypes exist, RNA from Louckes, a huma
n cell Line with the mature B-phenotype, was subjected to 5'-RACE anal
ysis. In addition to the two previously characterized mRNA forms. thre
e additional SIAT1 mRNA forms were identified. The new mRNA isoforms i
ncorporate novel sequence blocks into their 5'-UT regions. The data st
rongly suggest that these novel sequence blocks originate from previou
sly undocumented 5'-noncoding exons and are incorporated into mRNA by
alternative splicing events and/or usage of additional transcriptional
promoter regions. BLAST analysis reveals no similarity of these novel
regions, Exons U, V, and W, to sequences in GenBank. The only excepti
on is Exon V, which contains a portion of Alu, a repetitive element. T
he data suggest that two of these novel mRNA isotypes are likely to be
minor components. However, one form may contribute significantly to t
he SIAT1 mRNA pool in Louckes cells. (C) 1996 Academic Press, Inc.