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.

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.

Suppressive Effects of Divalent Cations on Self-splicing Inhibition by Spectinomycin of Group 1 Intron RNA: In Kook Park; J. Microbiol. 1999;37(4):243-247.

Abstract: Effects of divalent cations on self-splicing inhibition by the antibiotic spectinomycin of the phage T4 thymidylate synthase intro (td) have been investigated. Ca^2+ ion at 1mM concentration suppressed splicing inhibition of spectinomycin by 10% and 50 uM Co^2+ ion also suppressed splicing inhibition of specinomycin by 10%. Mg^2+ ion at 6 mM concentration decreased splicing inhibition of spectinomycin by 42% while Mn^2+ ion decreased the splicing inhibition by 10%. Zn^2+ ion at 10 uM concentration lowered the splicing inhibition by spectinomycin of 15%. Of all divalent cations tested, Mg^2+ ion was the most effective in suppressing splicing inhibition by specinomycin whereas Ca^2+ ion was the least effective. The results suggest that spectinomycin may interact with specific and functional Mg^2+ -binding sites within intron RNA that lead to a displacement of Mg^2+ essential for catalytic activity.

Effects of Thiamine Pyrophosphate on the Inhibition of Self-splicing of Primary Transcripts of T4 phage Thymidylate Synthase Gene in the Presence of GTP: Hyun Joo Lee , Sung Joon Ahn , Sook Shin , In Kook Park; J. Microbiol. 2002;40(2):134-139.

Abstract: Effects of GTP on the inhibition of self-splicing of primary transcripts of the phage T4 thymidylate synthase gene (td) by thiamine pyrophosphate and its analogs have been investigated. The order of the inhibitory efficiency for compounds tested was as follows: thiamine pyrophosphate > thiamine mono-phosphate > thiamine. Of all compounds examined, thiamine pyrophosphate was the most potent inhibitor. Increasing GTP concentration in splicing reaction tended to overcome the suppressive effects of self-splicing by thiamine pyrophosphate and its analogs. The inhibition by thiamine pyrophosphate was most sensitized to a higher concentration of GTP. It has been speculated that the key structural features in thiamine pyrophosphate and its analogs responsible for the inhibition of splicing may be a thiamine moiety in which the phosphorylation of 2-hydroxylethyl group on 5-position of thiazolium ring rendered further stimulation of inhibition in self-splicing reaction.

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