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D Apirion

Publications and source records attributed to D Apirion.

At least 55 records · Page 3Linked to original sources
PubMed1983

A gene affecting accumulation of the RNA moiety of the processing enzyme RNase P.

The level of 10Sb (M1) RNA, the RNA of RNase P, is very low in growing cultures of rnpB mutants. Northern transfer experiments suggested that these strains accumulate no more than 10% of the wild-type level of 10Sb RNA. However, there is no indication that there is a limiting amount of RNase P activity in these mutants in vivo. A plasmid that directs the synthesis of 10Sb RNA does not complement the rnpB mutants, even though there is only a single gene for 10Sb RNA in the Escherichia coli genome. The 10Sb RNA synthesized from this plasmid is equivalent to wild-type 10Sb RNA since it can replace it in the reconstitution of RNase P. The 10Sb RNA, which is a rather stable molecule, is unstable in the presence of the rnpB mutation. This could explain why rnpB mutants do not accumulate 10Sb RNA. An F' plasmid that contains DNA from the rnpB region of the chromosome complements an rnpB mutant in vivo and in vitro, and it also contains the 10Sb RNA gene. A number of possible explanations for these phenomena are discussed.

Endoribonucleases↗
PubMed1982

Primary and secondary structure in a precursor of 5 S rRNA.

In order to shed some light on the mechanism of action of RNAase E, we studied primary and secondary structure in 9 S (a precursor of 5 S rRNA), p5 and 5 S rRNAs. These molecules were digested with RNAases A and T1 in the presence of a high salt concentration; conditions under which single-stranded RNA is differentially digested. The double-stranded RNA fragments were isolated and analyzed. The analyses suggested that p5 and 5 S rRNA contain a stem of ten basepairs which consists of sequences from the 5' and 3' regions of the molecule, while 9 S contains a similar stem which is three basepairs longer and includes also a bulge of three unpaired bases. The stem in the 9 S RNA contains four sites where RNA processing cleavages occur. One of the cleavage sites which leads to the formation of p5 is in a junction between single-stranded and double-stranded RNA. The 9 S RNA molecule contains another large stem of at least 15 basepairs which is derived from the 3' end of the 9 S precursor molecular; it is apparently the transcription termination stem.

Base Sequence↗
PubMed1982

Ribonuclease E is involved in the processing of 5-S rRNA from a number of rRNA transcription units.

Strains of Escherichia coli having a thermosensitive RNase E produce a number of 5-S ribosomal RNA precursors at a non-permissive temperature. One of these precursors, 9-S RNA, was reported earlier [Ghora, B.K. and Apirion, D. (1978) Cell, 15, 1055-1066]. Here we show the existence of additional precursors to 5-S rRNA, originating from a number of rRNA genes. All the precursors are very similar in the first 200 nucleotides and the last part of this sequence contains the mature 5-S rRNA. Precursors that contain only these nucleotides (8-S RNA) accumulate. They probably originate from the rrn genes C, D and F which contain trailer tRNAs. The 9-S RNA precursors contain in addition a termination stem and loop structure and are derived from genes which do not contain trailer tRNA (Singh and Apirion, unpublished results). In addition, a 10-S precursor was identified. It contains distal to the 5-S rRNA a trailer tRNA, tRNAAsp, and a transcription termination signal. It is derived from the rrnF gene. The accumulation of an RNA precursor containing an RNase P site in an rne mutant suggests that the efficiency of one RNA processing enzyme depends on the activity of other RNA processing enzymes.

Base Composition↗
PubMed1982

A cleavage site of ribonuclease F. A putative processing endoribonuclease from Escherichia coli.

A new endoribonuclease activity, RNase F, was partially purified from Escherichia coli cells. This activity can specifically cleave a precursor RNA molecule (of species 1) isolated from T4-infected cells [N. Watson & D. Apirion (1981) Biochem. Biophys. Res. Commun. 103, 543-551]. The cleavage results in products which are very similar to RNA molecules found in the cell, generating a 3'-phosphate and a 5'-hydroxyl groups. The cleavage takes place between a cytosine and an adenine moiety, within a possible loop and stem structure; the cut is in the border between the double-stranded and single-stranded regions of this structure. This specificity of this enzyme could be the introduction of a cleavage near the 3' ends of tRNA molecules and other RNAs like species 1 which could resemble tRNA in their three-dimensional structure.

Base Sequence↗
PubMed1981

Transfer RNA precursors are accumulated in Escherichia coli in the absence of RNase E.

A temperature-sensitive Escherichia coli mutant, which contains a heat-labile RNase E, fails to produce 5-S rRNA at a non-permissive temperature. It accumulates a number of RNA molecules in the 4-12-S range. One of these molecules, a 9-S RNA, is a precursor to 5-S rRNA [Ghora, B. K. and Apirion, D. (1978) Cell, 15, 1055-1056]. These molecules were purified and processed in a cell-free system. Some of these RNA molecules, after processing, give rise to products the size of transfer RNA, but not to 5-S-rRNA. Further characterization of the processed products of one such precursor molecule shows that it contains tRNA1Leu and tRNA1His. RNase E is necessary but not sufficient for the processing of this molecule to mature tRNAs in vitro. The accumulation of such tRNA precursors in an RNase E mutant cell and the obligatory participation of RNase E in its processing indicate that RNase E functions in the maturation of transfer RNAs as well as of 5-S rRNA.

Base Sequence↗