2009年03月25日

telomerase RNA

Telomeres cap the ends of chromosomes and provide a means to complete replication. The DNA portion of telomeres is synthesized by the enzyme telomerase using part of an RNA subunit as a tenplate for reverse transcription. How the mature 3' end of telomerase RNA is generated has so far remained elusive.

Here we show that in Schizosaccharomyces pombe telomerase RNA transcriots must be rocessed to generate functional telomerase. Charecterization of the maturation pathway uncovered un unexpected role for the spliceosome, which normally catalyses splicing of pre-messenger RNA.

The first spliceosomal cleavage reaction generates the mature 3' end of telomerase RNA (TER1, the functional RNA encoded by the ter1^+ gene), releasing the active from of the RNA without exon ligation.

Blocking the first step or permitting completion of spllicing generates inactive forms of TER1 and causes progressive telomere shortening.

We establish that 3'end processing of TER1 is critical for telomerase function and describe a previously unknown mechanism for RNA maturation that uses the ability of the spliceosome to mediate site-specific cleavage.


### DataBace ###
nature Vol.456 837-1008 no.7224
Spliceosome meets tekimerase / Sophie Bonnal & Juan Valacarcel
Spliceosomal clavage generates the 3' end of telomerase RNA / J A Box et al. (Stowers Institure for Medical Research)

posted by 0≠素子 at 09:46| Comment(0) | biogeochemistry | このブログの読者になる | 更新情報をチェックする

2009年03月19日

Life before the rise of oxgen

The discovery og molecular fossils in 2.7-billion-year-old rocks prompted are-evaluation og microbial evolution, and of the advent of photosynthesis and rize of atmospheric oxgen.

That discovery now comes into question.


Go Back to Archaean time, the interval of Earth's History between about 4 billion and 2.5 bilion years ago, and we're in largely unknown biological territory.

Attenpts to identifly a fossil recorf of life have prodused meager ersults. and controversy presists obout whether certain microfossil-like structuress are of biological orgin.(Schopf,J.W.Phill Trans. R. Soc B.361-869-885/2006)(Brasier,M.D.et.al. Nature416,76-81/2002)

Almost a decade ago, however, Archaean palaeontology received a big boost with the discovery by Brocks et al. of a diverse assenblage og lipid 'biomarkers' in 2.7-billion year-old geological samples from Western Australia.

Biomarkers, or molecular fossils, are natural products (often hydrocarbons) whose synthesis can be linked to a specific biological origin - and, by physiological proxy, to enbiron mental conditions.

posted by 0≠素子 at 10:29| Comment(0) | biogeochemistry | このブログの読者になる | 更新情報をチェックする
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