Gene duplication and neofunctionalization: POLR3G and POLR3GL
- Marianne Renaud1,
- Viviane Praz1,
- Erwann Vieu1,
- Laurence Florens2,
- Michael P Washburn2,
- Philippe l'Hôte1 and
- Nouria Hernandez1,3
- ↵* Corresponding author; email: nouria.hernandez{at}unil.ch
Abstract
RNA polymerase III (pol III) occurs in two versions, one containing the POLR3G subunit and the other the closely related POLR3GL subunit. It is not clear whether these two pol III forms have the same function, in particular whether they recognize the same target genes. We show that the POLR3G and POLR3GL genes arose from a DNA-based gene duplication, probably in a common ancestor of vertebrates. POLR3G- as well as POLR3GL-containing pol III are present in cultured cell lines and in normal mouse liver, although the relative amounts of the two forms vary, with the POLR3G-containing pol III relatively more abundant in dividing cells. Genome-wide chromatin immuno-precipitations followed by high-throughput sequencing (ChIP-Seq) reveals that both forms of pol III occupy the same target genes, in very constant proportions within one cell line, suggesting that the two forms of pol III have similar function with regard to specificity for target genes. In contrast, the POLR3G, but not the POLR3GL, promoter binds the transcription factor MYC, as do all other promoters of genes encoding pol III subunits. Thus, the POLR3G/POLR3GL duplication did not lead to neo-functionalization of the gene product, at least with regard to target gene specificity, but rather to neo-functionalization of the transcription units, which have acquired different mechanisms of regulation, thus likely affording greater regulation potential to the cell.
- Received June 6, 2013.
- Accepted October 7, 2013.
- Published by Cold Spring Harbor Laboratory Press
This manuscript is Open Access.
This article, published in Genome Research, is available under a Creative Commons License (Attribution-NonCommercial 3.0 Unported), as described at http://creativecommons.org/licenses/by-nc/3.0/.
