Study of the transcriptional regulation of Arabidospis ASF1 histone chaperones by E2F factors

LUCIANA LARIO; PAULA CASATI; CLAUDIA P. SPAMPINATO; ELENA RAMIREZ-PARRA; CRISANTO GUTIERREZ

Tucumán

Congreso; XLV Reunión Annual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2009

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> ASF1 (anti-silencing function 1) is a conserved H3-H4 histone-chaperone first identified in yeast, which assembles or disassembles chromatin during transcription, replication and repair. In the Arabidopsis genome, two asf1 homologs, asf1a and asf1b, were identified, but their roles in plants have not been studied yet. Here, we show that these genes are targets of E2F transcription factors, which regulate the transcription of genes required for cell cycle progression and DNA replication. By bioinformatic tools, we identified the E2F DNA-binding sites in asf1a and asf1b promoters. Through electrophoretic mobility shift assays (EMSA), we found that Arabidopsis E2F proteins, can bind to these E2F sites in vitro. These results were confirmed by chromatin immunoprecipitation (ChIP) studies, demonstrating that E2F binds directly to the asf1a and asf1b promoters in vivo. Furthermore, transgenic Arabidopsis plants overexpressing different E2F proteins (such as E2Fa, E2Fb, E2Fd and E2Ff) showed increased asf1b expression. In addition, plants overexpressing the repressor of E2Fc or a dominant negative version of the essential dimerization partner of the Arabidopsis E2Fa, E2Fb and E2Fc proteins showed decreased asf1a and asf1b expression. These results clearly demonstrate that members of the E2F family can regulate asf1a and asf1b gene expression.