Kindy M S, McCormack J E, Buckler A J, Levine R A, Sonenshein G E
Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118.
Mol Cell Biol. 1987 Aug;7(8):2857-62. doi: 10.1128/mcb.7.8.2857-2862.1987.
Previously we demonstrated the existence of transcripts from the noncoding strand of a rearranged, truncated c-myc gene in murine plasmacytomas in which this oncogene is translocated to an immunoglobulin constant-region gene element (M. Dean, R. B. Kent, and G. E. Sonenshein, Nature [London] 305:443-446, 1983). Here we report on the transcription of the two strands of a normal, unrearranged c-myc gene. We examined the effects of gene rearrangements, growth state transitions, and differentiation on the relative levels of usage of the two strands. Transcription from intron 1 to exon 3 of the murine c-myc gene was studied in in vitro nuclear runoff assays. The level of transcription of the noncoding strand across this region of a germ line c-myc gene in a murine B-cell lymphoma line was comparable to the level observed in plasmacytomas with translocated c-myc genes. Rapid changes in transcription of the coding strand of the c-myc gene could be seen during growth arrest of WEHI 231 cells and during activation of splenic T lymphocytes. Transcription of the noncoding strand was constitutive during these growth state transitions and during activation of primary cultures of quiescent calf aortic smooth muscle cells as well. In contrast, differentiation of murine erythroleukemia cells was accompanied by an early drop in transcription of the two strands of this gene. The ramifications of these findings with respect to measurements of c-myc gene transcription and to the regulation of this gene are discussed.
此前我们已证明，在鼠浆细胞瘤中存在重排、截短的c-myc基因非编码链的转录本，在这些肿瘤中该癌基因易位至免疫球蛋白恒定区基因元件（M. 迪恩、R. B. 肯特和G. E. 索嫩申，《自然》[伦敦] 305:443 - 446，1983）。在此我们报告正常、未重排的c-myc基因两条链的转录情况。我们研究了基因重排、生长状态转变和分化对两条链相对使用水平的影响。在体外核延伸转录分析中研究了鼠c-myc基因从内含子1到外显子3的转录。在鼠B细胞淋巴瘤系中，生殖系c-myc基因该区域非编码链的转录水平与在c-myc基因易位的浆细胞瘤中观察到的水平相当。在WEHI 231细胞生长停滞期间以及脾T淋巴细胞激活期间，可以看到c-myc基因编码链转录的快速变化。在这些生长状态转变期间以及静止的小牛主动脉平滑肌细胞原代培养物激活期间，非编码链的转录都是组成型的。相反，鼠红白血病细胞的分化伴随着该基因两条链转录的早期下降。讨论了这些发现对于c-myc基因转录测量以及该基因调控的意义。
