Transient expression of TIP60 protein during early chick heart development

Abstract

Screening of an embryonic chick cDNA library revealed a gene product termed chick TIP60 (cTIP60) due to its homology with human TIP60, a founding member of the "MYST" family of proteins that possess functional motifs, including chromo, zinc finger, and histone acetyltransferase domains. cTIP60 expression was assessed during early chick embryogenesis, at the RNA level by using reverse transcriptase-polymerase chain reaction (RT-PCR) and at the protein level by using Western blotting and immunohistochemistry. RT-PCR indicated that cTIP60 transcripts in whole embryos are present as early as Hamburger-Hamilton (HH) stage 5, diminishing after HH10. Western blotting of total embryonic protein revealed that cTIP60 was present in uniform quantities between HH3 and HH25. By contrast, Western blotting of protein from isolated hearts revealed that cTIP60 protein was strongly expressed at the earliest stages of heart development (HH11-13), diminishing thereafter. This finding was corroborated by immunohistochemistry, which revealed that cTIP60 protein was selectively expressed at high levels in the myocardium between HH 10 -14. Considered in the context of its functional domains, these findings suggest that cTIP60 modulates transcriptional processes which regulate terminal cell differentiation, proliferation, or both, during early myocardial development.

Co-activation of Atrial Natriuretic Factor Promoter by Tip60 and Serum Response Factor

“…1 indicate that Tip60 protein expression is relatively strong at the earliest stages of heart development, confirming previous results in the chick embryo (12). Although the paucity of protein in hearts at these stages precluded Western blotting, our ongoing immunohistochemical and Western blotting determinations indicate that Tip60 protein is also relatively enriched in adult myocardium.…”

“…All procedures were as previously described (12). Controls included substitution of the primary antibody with a 1:50 dilution of normal rabbit IgG or preabsorption of primary antibody with 8 g of immunogenic peptide.…”

“…We previously reported that expression of Tip60 is developmentally regulated during early chick embryogenesis in a fashion highlighted by the transient enrichment of Tip protein in developing myocardium (12). It was therefore of interest to investigate whether Tip60 interacts with cardiac transcription factors to regulate cardiac gene expression.…”

Tip60 Is a Co-repressor for STAT3

“…Tip60 repressed reporter gene expression at a greater extent (up to 8-fold) in DF1 cells (Fig. 1C, columns [2][3][4][5], suggesting that the repressive effect of Tip60 is cell type-specific. In DF1 cells, the repressive effect of HAT-Tip60 was less than that of wild-type Tip60 (Fig.…”

Serum Response Factor, an Enriched Cardiac Mesoderm Obligatory Factor, Is a Downstream Gene Target for Tbx Genes

“…This inductive activity was lost when the T-box sites were mutated. In addition, it has recently been shown that TIP60, a founding member of the MYST family of histone acetyltransferases, appears in the embryonic chick myocardium and physically interacts with SRF (19). Although the function of TIP60 in the context of the early heart is unknown, we imagine that TIP60 may participate in the transcriptional regulation of early myocardial genes.…”