The ribosomal DNA plasmids of Entamoeba

被引:46
作者
Bhattacharya, S
Som, I
Bhattacharya, A
机构
[1] Jawaharlal Nehru Univ, Sch Environm Sci, New Delhi 110067, India
[2] Jawaharlal Nehru Univ, Sch Life Sci, New Delhi 110067, India
来源
PARASITOLOGY TODAY | 1998年 / 14卷 / 05期
关键词
D O I
10.1016/S0169-4758(98)01222-8
中图分类号
R38 [医学寄生虫学]; Q [生物科学];
学科分类号
07 ; 0710 ; 09 ; 100103 ;
摘要
In most organisms, the nuclear ribosomal RNA (rRNA) genes are highly repetitive and arranged as tandem repeats on one or more chromosomes. In Entamoeba, however, these genes are located almost exclusively on extrachromosomal circular DNA molecules with no clear evidence so far of a chromosomal copy. Such an uncommon location of rRNA genes may be a direct consequence of cellular physiology, as suggested by studies with Saccharomyces cerevisiae mutants in which the rDNA is extrachromosomal. lit this review, Sudha Bhattacharya, Indrani Som and Alok Bhattacharya summarize current knowledge on the structural organization and replication of the Entamoeba rDNA plasmids. Other than the rRNAs encoded by these molecules, no protein-coding genes (including ribosomal protein genes) are found on any of them. They are unique among plasmids in that they do not initiate replication from a fixed origin but use multiple sites dispersed throughout the molecule. Further studies should establish the unique biochemical features of Entamoeba that lead to extrachromosomal rDNA.
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页码:181 / 185
页数:5
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