Circular rDNA Replicons Persist inTetrahymena thermophilaTransformants Synthesizing GGGGTC Telomeric Repeats
作者:
DANIEL P. ROMERO,
ELIZABETH H. BLACKBURN,
期刊:
Journal of Eukaryotic Microbiology
(WILEY Available online 1995)
卷期:
Volume 42,
issue 1
页码: 32-43
ISSN:1066-5234
年代: 1995
DOI:10.1111/j.1550-7408.1995.tb01537.x
出版商: Blackwell Publishing Ltd
关键词: Ribosomal DNA replication;telomeres;telomerase;telomerase RNA
数据来源: WILEY
摘要:
ABSTRACTSite‐directed mutagenesis of the telomerase RNA fromTetrahymena thermophilawas used previously to demonstrate the templating function of a sequence within this RNA; this sequence specifies the sequence of telomeric DNA in vivo. The possible functional importance of a phylogenetically conserved nucleotide outside the telomerase RNA template region was investigated by a similar experimental approach. The telomerase RNA gene was altered by site‐directed mutagenesis, cloned in a circular selectable transformation vector consisting of an rRNA gene carrying a selectable drug resistance marker, and introduced into macronuclei of vegetatively dividingTetrahymena thermophilaby microinjection. Changing an invariant A to U at position 16 of the telomerase RNA (A16U) had no effect detectable by phenotype on telomerase function in vivo. However these experiments showed that a telomerase template alteration that dictates the synthesis of the mutant telomeric DNA sequence GGGGTC leads to a profound change in the population of rDNA replicons. The addition of GGGGTC mutant repeats leads to selective pressure for the loss of high copy linear rDNA, and the rRNA genes are maintained in the form of the circular rDNA replicons introduced during transformat
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