Lin E S, Wilson D B
Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853.
J Bacteriol. 1988 Sep;170(9):3838-42. doi: 10.1128/jb.170.9.3838-3842.1988.
The steady-state level of celE mRNA (coding for cellulase E5) in Thermomonospora fusca YX was measured by Northern (RNA blot) hybridization under conditions causing induction or repression of cellulase synthesis. A good correlation was found between the mRNA level and the level of cellulase E5, suggesting that the T. fusca celE gene is regulated at the level of mRNA and, most likely, at the level of transcription. The 5' and 3' ends of the celE gene transcription unit were determined by S1 mapping with single-stranded DNA probes. These results showed that there were three species of celE mRNA in T. fusca YX with closely spaced 5' ends and identical 3' ends. The size of each mRNA was about 1.5 kilobases, from both the Northern and S1 data. This size is only slightly longer than that required to code for the 45-kilodalton E5 protein. In Escherichia coli D318 (celE), the 5' ends of the celE mRNAs are identical to those in T. fusca, but the 3' ends are located ca. 300 base pairs upstream of the T. fusca 3' end. The region where the putative celE promoters were located had some interesting features, including a 60-base-pair A + T-rich sequence and sequences resembling sigma 60 promoters.
在导致纤维素酶合成诱导或抑制的条件下，通过Northern（RNA印迹）杂交法测定了嗜热栖热放线菌YX中celE mRNA（编码纤维素酶E5）的稳态水平。发现mRNA水平与纤维素酶E5水平之间具有良好的相关性，这表明嗜热栖热放线菌celE基因在mRNA水平上受到调控，很可能是在转录水平上。通过用单链DNA探针进行S1作图确定了celE基因转录单位的5'和3'末端。这些结果表明，嗜热栖热放线菌YX中有三种celE mRNA，其5'末端间隔紧密，3'末端相同。根据Northern和S1数据，每种mRNA的大小约为1.5千碱基。这个大小仅比编码45千道尔顿E5蛋白所需的大小略长。在大肠杆菌D318（celE）中，celE mRNA的5'末端与嗜热栖热放线菌中的相同，但3'末端位于嗜热栖热放线菌3'末端上游约300个碱基对处。推测的celE启动子所在区域具有一些有趣的特征，包括一个60个碱基对的富含A+T的序列和类似于σ60启动子的序列。
