Abstract
Gene transcription in eukaryotes is modulated by the coordinated recruitment of specific transcription factors and chromatin-modulating proteins. Indeed, gene activation and/or repression is/are regulated by histone methylation status at specific arginine or lysine residues. In this work, by co-immunoprecipitation experiments, we demonstrate that PRMT5, a type II protein arginine methyltransferase that monomethylates and symmetrically dimethylates arginine residues, is physically associated with the Kruppel-like associated box-zinc finger protein ZNF224, the aldolase A gene repressor. Moreover, chromatin immunoprecipitation assays show that PRMT5 is recruited to the L-type aldolase A promoter and that methylation of the nucleosomes that surround the L-type promoter region occurs in vivo on the arginine 3 of histone H4. Consistent with its association to the ZNF224 repressor complex, the decrease of PRMT5 expression produced by RNA interference positively affects L-type aldolase A promoter transcription. Finally, the alternating occupancy of the L-type aldolase A promoter by the ZNF224-PRMT5 repression complex in proliferating and growth-arrested cells suggests that these regulatory proteins play a significant role during the cell cycle modulation of human aldolase A gene expression. Our data represent the first experimental evidence that protein arginine methylation plays a role in ZNF224-mediated transcriptional repression and provide novel insight into the chromatin modifications required for repression of gene transcription by Kruppel-like associated box-zinc finger proteins.