Session: SUN 17-28-Adrenal Tumors & Pheochromocytoma
Poster Board SUN-22
To investigate the mechanisms involved in dosage-dependent regulation of gene expression by SF-1, we have identified its sites of binding to chromatin in conditions of basal and increased dosage using chromatin immunoprecipitation coupled to high-throughput sequencing (ChIP-seq) in our H295R cell model where SF-1 overexpression can be triggered by doxycycline treatment (Doghman et al., Mol. Endocrinol. 21: 2968-2987, 2007). In conditions of basal expression, SF-1 bound to about 4000 distinct sites in chromatin. Only 17.7% of these sites are located inside or in the proximity (±10 kb) of known genes. Strikingly, in conditions of SF-1 overexpression, the number of sites bound in chromatin was nearly tripled, 32.7% of which lies in the proximity of genes. Expression profiling showed that 708 genes are upregulated ≥2-fold, while 676 genes are down-regulated ≥2-fold when SF-1 is overexpressed. A significant overlap exists between genes bound by SF-1 only when overexpressed and upregulated genes, while the correlation is not significant between genes bound by SF-1 only when overexpressed and downregulated genes. These data suggest that SF-1 has a direct activating function on genes upregulated when the factor is overexpressed, while its negative effects on gene expression are probably indirect. By motif analysis, we could find the consensus SF-1 binding sequence (CAAGGTCA) and/or its variants in bound sites. This sequence was also significantly enriched in chromatin sites bound by SF-1 in primary ACC samples. Other predicted transcription factor binding sequences were also significantly enriched in SF-1 bound DNA. Based on this data, further work is in progress to elucidate the mechanisms of regulation of gene expression by SF-1 in a dosage-dependent fashion.
Nothing to Disclose: EL, MD, BCF, MV, MP
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