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Research Papers
1 Section of Plant Biology, Cornell University, Itchaca, New York 14853-5908 USA , 2 Division of Neonatal, Department of Pediatrics, University of Rochester Medical Center, Rochester, New York 14627 USA , Department of Biology, University of Rochester, New York 14627 USA
Abstract
The H4 multigene family of Tetrahymena thermophila consists of two genes that code for identical proteins. A quantitative, dot-blot method applicable to intact cells was used to develop techniques for analyzing expression of these (or any other) genes during the cell cycle and in nongrowing cells. Cell cycle stages were determined by cytological analysis of nonsynchronized, growing cells. Upon in situ hybridization with gene-specific probes, both H4-I and H4-II are found to be expressed during macronuclear S phase but only H4-II is expressed during micronuclear S. The amount of H4-II mRNA per cell during micronuclear S is considerably less than during macronuclear S. The relative amounts of both mRNAs are reduced about 20- to 30-fold in nongrowing (starved) cells. Thus, the expression of these two genes can be either coordinate or independent, and both genes function in histone replication and in histone replacement. These results demonstrate that surprising complexity in expression of housekeeping genes can be achieved with an extremely small number of genes in a unicellular eukaryote.
[Keywords: Multigene families; cell cycle; histone genes; in situ hybridization]
Received May 11, 1987; revised version accepted June 30, 1987.
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