MULTIPLE TRANSCRIPTS FOR RAT NUCLEOSIDE DIPHOSPHATE KINASE ALPHA-ISOFORM ARE STRUCTURALLY CATEGORIZED INTO 2 GROUPS THAT EXHIBIT CELL-SPECIFIC EXPRESSION AND DISTINCT TRANSLATION POTENTIAL
N. Ishikawa et al., MULTIPLE TRANSCRIPTS FOR RAT NUCLEOSIDE DIPHOSPHATE KINASE ALPHA-ISOFORM ARE STRUCTURALLY CATEGORIZED INTO 2 GROUPS THAT EXHIBIT CELL-SPECIFIC EXPRESSION AND DISTINCT TRANSLATION POTENTIAL, The Journal of biological chemistry, 272(6), 1997, pp. 3289-3295
Rat nucleoside diphosphate (NDP) kinase is composed of two isoforms (a
lpha and beta) encoded by independent genes. The mRNAs are expressed u
biquitously; however, the level of expression is tissue-dependent and
is also up- or down-regulated under certain conditions, including grow
th stimulation, differentiation, and tumor metastasis. To address the
regulatory mechanisms of gene expression for the rat NDP kinase major
isoform alpha (an nm23-H2/PuF homologue), we identified the transcript
ion initiation sites in detail by RNase protection and 5'-rapid amplif
ication of DNA ends and located the core promoter region by chloramphe
nicol acetyltransferase assay. The transcripts, initiated from an extr
aordinarily wide range of sites, were categorized into two groups; one
transcribed from an upstream region was spliced in the untranslated r
egion (group 1), whereas the other initiated in the downstream region
was not (group 2). RNase protection demonstrated that the group 1 mRNA
was the dominant form present in all tissues except heart and skeleta
l muscle. In situ hybridization revealed cell specific expression of t
hese mRNA species, Furthermore, they differed in the translational eff
iciency (the group 2 alpha > beta > the group 1 alpha). These findings
suggest that the regulation of the NDP kinase expression at both tran
scriptional and posttranscriptional steps could be fundamentally gover
ned by the selection of transcription initiation sites.