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TOBFAC: The database of tobacco transcription factors

Family: PcG

Minimum number of tobacco PcG genes: 20

Count of tobacco PcG sequences: 39

Pfam accession:

Polycomb group (PcG) proteins maintain silencing at target loci in higher eukaryotes but recent evidence suggests that about half of these proteins are also required for maintenance of activation at homeotic loci.

The best-studied proteins required for the maintenance but not initiation of repression of target loci are encoded by genes of the Polycomb group (PcG). PcG mutants exhibit posterior transformations in embryos and adults caused by derepression of homeotic loci in flies [1], and in vertebrates [2]. In addition, PcG genes regulate non-homeotic targets. In contrast, proteins of the trithorax group (trxG) are required for maintenance but not initiation of activation of homeotic loci [3]. Many genes in the trxG were identified because they suppress phenotypes of PcG mutations, suggesting that the trxG proteins act antagonistically to PcG proteins [4]. Structural analysis of PcG and trxG response elements shows that the elements required for trxG-dependent activation and PcG-dependent repression are separable but within 30¨C40 bp of each other. This intermingling of elements required for activation and repression in DNA sequences previously termed PcG response elements (PREs) or trxG response elements (TREs) leads us to propose that DNA sequences required for maintenance of gene regulation be named ¡®maintenance elements¡¯ in recognition of their dual function. How maintenance of gene expression is achieved is unknown at present but new evidence supports the idea that there may be overlap between mechanisms of PcG and trxG modification of chromatin and the chromatin condensation that occurs prior to mitosis.

Papers

Brock HW, van Lohuizen M. The Polycomb group--no longer an exclusive club? Curr Opin Genet Dev. 2001 Apr;11(2):175-81. PMID: 11250141

Number of contigs: 25

Number of singlets: 21

Number of N terminal – 9

Number of C terminal – 14

Number of full – 6

Number of genes with middle bit – 10

Total minimum number – 20

Search sequences and info

Transcription factor sequences

Tobacco published genes related to transcription factor family PcG

Authors of this site:

Paul J Rushton
Marta T. Bokowiec
Xianfeng (Jeff) Chen
Thomas (Tom) W Laudeman
Jennifer F. Brannock
Michael P. Timko

Contact:

pr8y@virginia.edu