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Mol Biol Cell 2002 Oct 01;1310:3466-76. doi: 10.1091/mbc.e02-05-0281.
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RNA polymerase III in Cajal bodies and lampbrush chromosomes of the Xenopus oocyte nucleus.

Murphy C , Wang Z , Roeder RG , Gall JG .

We used immunofluorescence to study the distribution and targeting of RNA polymerase (pol) III subunits and pol III transcription factors in the Xenopus laevis oocyte nucleus. Antibodies against several of these proteins stained Cajal bodies and approximately 90 specific sites on the lampbrush chromosomes. Some of the chromosomal sites had been identified previously by in situ hybridization as the genes for 5S rRNA. The remaining sites presumably encode tRNAs and other pol III transcripts. Pol III sites were often resolvable as loops similar to the much more abundant pol II loops, but without a matrix detectable by phase contrast or differential interference contrast. This morphology is consistent with the transcription of short repeated sequences. Hemagglutinin-tagged transcripts encoding core subunits and transcription factors were injected into the oocyte cytoplasm, and the distribution of newly translated proteins inside the nucleus was monitored by immunostaining. Cajal bodies were preferentially targeted by these proteins, and in some cases the chromosomal sites were also weakly stained. The existence of pol III subunits and pol III transcription factors in Cajal bodies and their targeting to these organelles are consistent with a model of Cajal bodies as sites for preassembly of the nuclear transcription machinery.

PubMed ID: 12388750
PMC ID: PMC129959
Article link: Mol Biol Cell
Grant support: [+]

Species referenced: Xenopus laevis
Antibodies: Bdp1 Ab1 Pol3rc Ab1 Polr2f Ab1 Polr2f Ab2 Polr3d Ab1 Polr3d Ab2 Polr3f Ab1

References [+] :
Acker, A 14.4 KDa acidic subunit of human RNA polymerase II with a putative leucine-zipper. 1994, Pubmed