p300 protein as a coactivator of GATA-5 in the transcription of cardiac-restricted atrial natriuretic factor gene.

A cellular target of adenovirus E1A oncoprotein, p300 is a transcriptional coactivator and a negative regulator of cellular proliferation. A previous study suggests that the p300 family is also involved in cell type-specific transcription in cardiac myocytes. However, nothing is known about which cardiac transcription factor(s) interact with and transactivate through these proteins. The transcription factors GATA-4/5/6 have been implicated as key regulators of cardiogenesis, and they participate in the transcription of many cardiac-specific genes. Here we show that E1A represses the GATA-5-dependent transactivation of a promoter derived from the cardiac-restricted atrial natriuretic factor gene. This repression is correlated with the interaction of E1A with p300, indicating that p300 participates in GATA-5-dependent transactivation. E1A markedly down-regulates endogenous atrial natriuretic factor expression, as well as disrupts the interaction between p300 and GATA-5. A small fragment of p300 containing the carboxyl-terminal cysteine/histidine-rich domain, sufficient to interact with GATA-5, prevents transcriptional activation by GATA-5 as a dominant-negative mutant. Consistent with its role as a coactivator, p300 markedly potentiates GATA-5-activated transcription. These results implicate p300 as an important component of myocardial cell differentiation and provide an insight into the relationship between mechanisms that mediate cell type-specific transcription and cell cycle regulation during cardiogenesis.