Sequence of LTR of mouse mammary tumor virus and its regulatory factors

1)克隆了乳腺肿瘤高发株SHN小鼠体内内源性小鼠乳腺肿瘤病毒(MMTV)的长末端重复序列，并对其序列进行了分析。在280-380密码子之间的开放阅读框中，与已报道的小鼠MMTV序列相比，发现了许多碱基变化。2)MMTV DNA以染色体外DNA片段的形式存在于皮肤中，并被证明是完整的MMTV基因组。然而，它在MMTV复制过程中的作用尚不清楚。3)众所周知，能量限制(ER)抑制了MMTV的基因表达，尽管其机制尚不清楚。我们发现内质网诱导了昏迷，进而抑制了不同器官中的细胞增殖。然而，增加能量消耗或提高温度可以缓解抑制。4)我们发现ER特异性地减少了RNA总量和细胞数量。然而，ER对PRL mRNA的抑制程度远大于肌动蛋白mRNA，表明PRL mRNA的降低幅度比其他基因更大。5)微粒体AA^&lt；+&Gt；-ATPase活性在ER后降低。在常温体温下，脑、肝脏和唾液腺以及这些和肾脏中的活性在恒温体温下降低。

In the present project, the following findings were made.1) The long terminal repeat (LTR) of endogenous mouse mammary tumor virus (MMTV) in the SHN mouse strain, known to have a high incidence of mammary tumors, was cloned and its sequence was elucidated. In the open reading frame between 280 and 380 codons, many base changes were found when compared with reported murine MMTV sequences. In contrast, the sequence of regulatory area of the present LTR was well preserved.2) The MMTV DNA was found to exist as extrachromosomal DNA fragments in the skin and was proven that it is an entire whole MMTV genome. Its role in the MMTV replicating processes, however, remains unknown.3) It has been known that energy restriction (ER) suppresses gene expression of MMTV, although its mechanisms still remains unknown. We found that ER induced torpor and it, in turn, suppressed cellular proliferation in various organs. Suppression, however, was alleviated by increases in energy consumption or in housing temperatures.4) We found that ER decreased the total amount of RNA specifically as well as numbers of cells. PRL mRNA was, however, decreased by ER to much greater extent than that in actin mRNA, suggesting that PRL mRNA decreased more profoundly than other genes.5) Activities of microsomal Aa^<++>-ATPase was found to be decreased after ER.Their activities were found to be decreased at euthermic body temperatures in brain, liver, and salivary glands, and in these and kidney at heterothermic body temperatures.