Journal of Microbiology

Role of Mg^2+ in RNA Splicing of T4 td Intron: Sung, Jung Suk , Shin, Sookc , Park, In Kook; J. Microbiol. 1995;33(2):160-164.

Abstract: The splicing activity of T4 phage td intron RNA has been examined with various Mg^2+ ions such as MgCl₂, MgSO₄and magnesium acetate using various splicing conditions such as different incubation time and temperature. The maximum splicing of td intron RNA occurred at the concentration of 5 mM MgCl₂. Raising the Mg^2+ concentration up to 15 mM appeared to promote P2 delection mutant to overcome the loss of some splicing activity. In both wild type and mutant, a complete hydrolysis of RNA occurred at 30 mM MgCI₂MgSO₄and magnesium acetate exhibited the rate and pattern of RNA splicing identical to MgCI₂. The optimal splicing conditions involve the incubation of RNA with 5 mM MgCI₂ at 58℃ for 15 min. The results suggest that Mg^2+ may play a key role in the catalytic mechanism of td intron RNA.

Mutational analysis of P2 structure in T4 phage td intron: Shin, sook , Park, In kook; J. Microbiol. 1995;33(1):91-94.

Abstract: The functional role of P2 stem-loop structure of T4 td intron in splicing in vivo and in vitro was investigated. Site-directed mutagenesis was employed to create the subtitution, deletion and reversion mutants of P2 stem=loop structure. Two substitution mutation(U16→G, A31→C) and on deletion mutation (G21□C26) resulted in a complete loss of enzyme activity whereas the compensatory double mutation restored about 82% of activity of the wild type. The transcription rate of two substitution mutations and P2 loop deletion is lower than that of the wild type. The disruption of P2 stem-loop structure by introducing substitution and deletion mutation resulted in a complete abolishment of Rna splicing in bitro. However, a compensatory double mutation showed splicing activity very similar to the wild type.

Effects of K^+ lon on in vitro RNA splicing of T4 phage thymidylate synthase gene: Sung, Jung Suk , Park, In Kook; J. Microbiol. 1996;34(1):49-53.

Abstract: The effects of K^+ ion on the activity of RNA splicing of T4 phage thymidylate synthase gene have been investigated. The splicing activity was stimulated within the range of 5 to 20 mM concentration of KCI. When the concentration of KCI in the splicing reaction was brought to 100 or 200 mM a small amount of the exonl-intron product (1, 4 kb) was formed with large proportion of primary RNA transcript not undergoing splicing. This observation strongly suggests that there may exist come kinds of interferences with transesterification at the first step of splicing. Overall it can be concluded that K^+ ion exhibits very unique roles in RNA splicing of td gene depending on its concentration.

Isolation and characterization of pre-tRNA^Val splicing Mutants of Schizosaccharomyces pombe: Hwang, Ku Chan , Kim, Dae Myung; J. Microbiol. 1997;35(4):334-340.

Abstract: A collection of 132 temperature sensitive (ts) mutants was generated by the chemical mutagenesis of Schizosaccharomyces pombe wild type strain and screened for tRNA splicing defects on Northern blots by hybridization with an oligonucleotide that recognizes the exon of the S. pombe tRNA^Val as a probe. We identidied 6 mutants which accumulate precursor tRNA^Val. Among them, 2 mutants exhibited remarkable morphological differences compared to wild type cells. One tRNA splicing mutant showed elongated cell shape in permissive as well as non-permissive cultures. The other mutant exhibited shortened cell morphology only in nonpermissive culture. The total RNA pattern in the splicing mutants appeared to be normal. Genetic analysis of four tRNA^Val splicing mutants demonstrated that the mutation reside in different genes.

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