| Abstract [eng] |
Phage T4 has developed a complex mechanism of ribonucleases control, which needs yet to be investigated. Apart from the impact of endoribonuclease RegB, no other effects of Escherichia coli- or phage-encoded proteins are known to be involved in the degradation of early mRNAs. This study has aimed to identify E. coli endoribonucleases that are involved in secondary processing in RegB-cleaved T4 mRNAs and to determine what phage T4-encoded factors affect the activity of these enzymes. We have shown that the endonucleolytic events at secondary sites of RegB-processed transcripts involve RNases G and E. The RNase G appears to be the main ribonuclease that cleaves all known secondary targets. Moreover, the revealed targets are the first RNase G targets identified in the bacteriophage T4 mRNA. This study has revealed that RNase G can be covalently modified during the infection cycle of bacteriophage T4. However, such modifications do not affect its activity related to the origin of secondary cuts in RegB-processed T4 mRNA. Another important finding is that T4K10 phage encodes defective polynucleotidkinase (PNK). In this study, we have shown that the G14D mutation of phage T4K10 PNK impairs 5'-kinase activity in vivo, as well as in vitro, and leads to the diminished processing of RegB-cleaved transcripts. This study has revealed that both, the T4 RNase RegB- and PNK-mediated activity of the E. coli RNases E and G is designed to accelerate degradation of phage T4 early transcripts. |
