Kim K K, Soonpaa M H, Wang H, Field L J
Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis 46202-4800, USA.
Genomics. 1995 Aug 10;28(3):520-9. doi: 10.1006/geno.1995.1184.
Expression of p107, a protein with homology to the retinoblastoma tumor suppressor (pRB), was monitored during murine development. Northern blot tissue surveys identified two transcripts of 4.9 and 2.4 kb that hybridized to a p107 cDNA clone. Expression of both transcripts was detected in fetal tissues, with particularly high levels in the liver and heart. In contrast, p107 transcripts were markedly decreased in most adult tissues examined. Molecular cloning analyses revealed that the 4.9- and 2.4-kb transcripts encoded proteins with deduced molecular masses of 119 and 68 kDa, respectively. Genetic mapping studies suggested that the two p107 transcripts arose by alternative splicing of a common precursor. The protein encoded by the 2.4-kb transcript lacks the spacer and B motif of the "pocket domain," a region of homology between p107 and pRB that is required for binding to cell cycle regulatory proteins. Structural modifications resulting from alternative splicing may thus confer functional diversity upon the 119- and 68-kDa proteins.
在小鼠发育过程中监测了与视网膜母细胞瘤肿瘤抑制蛋白（pRB）具有同源性的p107蛋白的表达。Northern印迹组织检测鉴定出与p107 cDNA克隆杂交的4.9 kb和2.4 kb两种转录本。在胎儿组织中检测到两种转录本的表达，在肝脏和心脏中水平尤其高。相比之下，在所检测的大多数成年组织中p107转录本明显减少。分子克隆分析表明，4.9 kb和2.4 kb的转录本分别编码推导分子量为119 kDa和68 kDa的蛋白质。遗传图谱研究表明，两种p107转录本是由一个共同前体的可变剪接产生的。2.4 kb转录本编码的蛋白质缺乏“口袋结构域”的间隔区和B基序，p107和pRB之间的这个同源区域是与细胞周期调节蛋白结合所必需的。因此，可变剪接导致的结构修饰可能赋予119 kDa和68 kDa蛋白质功能多样性。
