The human Pim-1 gene is selectively transcribed in different hemato-lymphoid cell lines in spite of a G + C-rich housekeeping promoter.
The expression of the Pim-1 proto-oncogene was studied by using the K562, Daudi, and Jurkat cell lines. In K562, Pim-1 mRNA levels were more than 20-fold higher than in Daudi and 50-fold higher than in Jurkat. Nuclear run-on assay data correlated directly with the steady-state mRNA levels, suggesting that the rate of transcription was responsible for the selective expression of this gene. Furthermore, the half-life of Pim-1 mRNA was shown to be 47 min in K562, 71 min in Daudi, and 35 min in Jurkat. This indicated that selective Pim-1 mRNA expression did not depend on posttranscriptional regulation. Therefore, 1.7 kilobases of the Pim-1 promoter was sequenced and studied in detail. The sequence showed that the region from nucleotide -1 to -873 was G + C rich (71%). Study of promoter deletions defined two major functional regions, a proximal element (nucleotide -104 to -1) and a distal element (nucleotide -427 to -336). DNase I protection assays identified binding sites for the Sp1 and AP2 proteins in these elements. A possible new transcription factor binds at position -348 in the distal element. In our study of the 1.7-kilobase Pim-1 promoter, we found no differences between K562 and Jurkat that could explain large differences in transcription. Therefore, the Pim-1 promoter appears to function constitutively, and we conclude that distant elements must regulate the tissue-selective expression of this gene. Although the Pim-1 gene has a G + C-rich housekeeping promoter, expression is carefully regulated at the level of transcription.
Meeker
T C
TC
Department of Medicine, University of California, San Francisco.
Loeb
J
J
Ayres
M
M
Sellers
W
W
D001482:Base Composition; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D004273:DNA, Neoplasm / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051573:Proto-Oncogene Proteins c-pim-1; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured / Q000201:enzymology
D004273:DNA, Neoplasm; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011505:Protein-Tyrosine Kinases; C496634:PIM1 protein, human; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1