ISSN:
0730-2312
Keywords:
5-bromouridine 5′-triphosphate
;
electron microscopy
;
domain
;
nuclear matrix
;
RNA polymerase II
;
transcription
;
ultrasmall gold
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
We have studied the ultrastructural localization of active genes in nuclei of the human epidermoid carcinoma cell line A431. Nascent RNA was labeled by incorporation of 5-bromouridine 5′-triphosphate, followed by pre-embedment or postembedment immunogold labeling and electron microscopy using ultrasmall gold-conjugated antibodies and silver enhancement. This combination of techniques allowed a sensitive and high resolution visualization of RNA synthesis in the nucleus. Transcription sites were identified as clusters of 3-20 gold particles and were found throughout the nucleoplasm. The clusters had a diameter of less than 200 nm. The distribution of clusters of gold particles in nuclei is preserved in nuclear matrix preparations. Nascent RNA is associated with fibrillar as well as with granular structures in the matrix. A431 nuclei contained on average about 10,000 clusters of gold particles. This means that each cluster represents transcription of probably one active gene or, at most, a few genes. Our study does not provide evidence for aggregation of active genes. We found transcription sites distributed predominantly on the surface of electron-dense nuclear material, probably lumps of chromatin. This supports a model of transcription activation preferentially on the boundary between a chromosome domain and the interchromatin space. © 1996 Wiley-Liss, Inc.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
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