BACTERIOPHAGE-P2 LATE PROMOTERS .2. COMPARISON OF THE 4 LATE PROMOTER SEQUENCES
BACTERIOPHAGE-P2 LATE PROMOTERS .2. COMPARISON OF THE 4 LATE PROMOTER SEQUENCES
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DOI：
10.1016/0022-2836(85)90226-8
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发表时间：
1985-01-01
影响因子：
5.6
通讯作者：
CALENDAR, R
中科院分区：
文献类型：
--
作者：
CHRISTIE, GE;CALENDAR, R
噬菌体P2的晚期基因聚为4个转录单位。编码基因QP和ONMLKRS的2个晚期基因的转录起始点已有报道。剩下的2个晚期信使核糖核酸的5‘’末端现在被定位了。通过对V琥珀突变体单核苷酸变化的DNA序列测定，定位到VJHG转录单位的第一个基因。根据DNA序列推测第一个基因在FETUD转录单元中的位置。在RNA-DNA杂交物中，通过末端标记的限制性片段保护这两个转录单位的mRNA5‘’末端不被核酸酶S1消化。用5‘端标记有[α-32P]GTP和鸟苷酸转移酶的RNA对杂交种的保护作用相似，证实这些5’端是转录启动的结果。在P2晚期转录开始之前的DNA序列不同于大肠杆菌启动子-10和-35的共同序列，这与噬菌体编码蛋白在调节P2晚期基因表达方面的明显要求是一致的。4个P2晚期启动子确实在-10和-35区域有序列同源性，并且在上游还有几个额外的同源性。P2晚期基因的表达似乎也涉及到ONMLKRS基因簇的产物的负调控。当细胞感染P2极性O琥珀突变体时，观察到其他3个基因簇编码的蛋白质水平显著增加。这种增加反映在晚期mRNA的数量上，这表明RNA合成通常受到抑制，或者在ONMLKRS转录单元的基因产物存在的情况下，晚期mRNA更不稳定。卫星噬菌体P4诱导P2晚期基因表达，而不需要P2DNA复制。在P4反式激活过程中，P2晚期基因的5‘端与正常P2晚期基因表达时的5’端相同。因此，P4对P2晚期基因表达的调节不涉及改变启动子的选择。
The late genes of bacteriophage P2 are clustered into 4 transcription units. The transcription initiation sites for 2 of the late mRNA, encoding genes QP and ONMLKRS were previously reported. The 5'' ends of the 2 remaining late mRNA are now located. The 1st gene in the VJHG transcription unit was located by DNA sequence determination of the single nucleotide change in a V amber mutant. Location of the 1st gene in the FETUD transcription unit was inferred from the DNA sequence. The 5'' ends of the mRNA for these 2 transcription units were located by protection of end-labeled restriction fragments in RNA-DNA hybrids from digestion with nuclease S1. Similar protection of hybrids using RNA that was 5'' end-labeled with [.alpha.-32P]GTP and guanylyl transferase confirmed that these 5'' termini resulted from initiation of transcription. The DNA sequences preceding the P2 late transcription starts are different from the Escherichia coli promoter consensus sequences at -10 and -35, consistent with the apparent requirement for phage-encoded proteins in the regulation of P2 late gene expression. The 4 P2 late promoters do share sequence homologies in the -10 and -35 regions and several additional homologies further upstream. P2 late gene expression also appears to involve negative regulation by a product of the ONMLKRS gene cluster. When cells are infected with P2 polar O amber mutants, a marked increase in the levels of proteins encoded by the other 3 gene clusters is observed. This increase is reflected in the amounts of late mRNA, suggesting that RNA synthesis is normally repressed or that late mRNA are more labile in the presence of a gene product from the ONMLKRS transcription unit. Satellite phage P4 induces P2 late gene expression without the usual requirement for P2 DNA replication. The 5'' ends of the P2 late mRNA are the same during P4 transactivation as during normal P2 late gene expression. Thus, the regulation of P2 late gene expression by P4 does not involve altered promoter selection.