FACTORS INFLUENCING GENETIC TRANSCRIPTION-INITIATION AND TERMINATION

细菌和逆转录病毒的核糖核酸酶H已被检测 对于酶活性而言，当氨基或羧基末端 都被更改了。氨基酸在氨基半胱氨酸上的加成 鼠伤寒沙门氏菌核糖核酸酶H对其特异性影响不大。 蛋白质的活性以及少量的羧基缺失 终点站。相反，去除三分之一的羧基 AKRMuLV逆转录酶的核糖核酸酶H部分 显著降低了RNaseH的活性，但没有任何显著的 聚合酶活性的改变。取代硒- 在大肠杆菌中蛋氨酸为蛋氨酸。核糖核酸酶H似乎没有 更改活动。 酵母RRP1基因的信使核糖核酸具有三种不寻常的特性： 1)有一个很长的(对于酵母)3‘-非翻译区2)水平 随着细胞密度的增加而减少；3)存在 RRP1基因3‘末端序列与DNA的重叠 一个更为丰富的0.6kb碱基mRNA的5‘末端。两国关系 这些不寻常的特征对RRP1功能的影响 蛋白质仍然未知，但表明RRP1蛋白可能是 对调节核糖体前核糖体RNA转换量的重要作用 成熟的rRNA。

Ribonucleases H from bacteria and retroviruses have been examined for enzymatic activity when either the amino or carboxyl termini were altered. Addition of amino acids at the amino terntinus of Salmonella typhimurium RNase H had little effect on the specific activity of the protein as did a small deletion of the carboxyl terminus. In contrast, removal of the carboxyl one third of the RNase H portion of the AKRMuLV reverse transcriptase RNase H dramatically decreased the RNase H activity without any significant alteration of the polymerase activity. Substitution of seleno- methionine for methionine in E. coli. RNase H does not seem to alter the activity. The mRNA from the RRP1 gene of yeast has three unusual properties: 1) there is a long (for yeast) 3'-untranslated region 2) the level of mRNA decreases as the cell density increases and 3) there is an overlap of sequence of the 3'-terminus of the RRP1 mRNA with the 5'-terminus of a more abundant 0.6 kilobase mRNA. The relationship of these unusual characteristics to the function of the RRP1 protein remain unknown but suggest that the RRP1 protein may be important in regulating the amount of pre-ribosomal RNA converted to mature rRNA.