The histone acetyltransferase TIP60 interacts with c-Myb and inactivates its transcriptional activity in human...

Area of Science:

• * Molecular biology
• * Cancer research
• * Hematopoiesis

Background:

• * The histone acetyltransferase TIP60 is a known transcriptional co-regulator implicated in cancer.
• * The c-Myb oncoprotein plays a critical role in hematopoietic cell development and is often dysregulated in leukemia.
• * Understanding the interplay between TIP60 and c-Myb is crucial for elucidating mechanisms of leukemogenesis.

Purpose of the Study:

• * To investigate the regulatory relationship between TIP60 and the c-Myb oncoprotein in human hematopoietic cells.
• * To determine if TIP60 modulates c-Myb's transcriptional activity and its potential role in acute myeloid leukemia (AML).

Main Methods:

• * Co-immunoprecipitation and yeast two-hybrid assays to confirm TIP60-c-Myb interaction.
• * Reporter gene assays to assess the impact of TIP60 on c-Myb transcriptional activity.
• * Chromatin immunoprecipitation (ChIP) assays to evaluate TIP60 binding to c-Myb target genes.
• * siRNA-mediated knockdown of TIP60 and quantitative RT-PCR to measure gene expression changes.
• * Comparison of TIP60 expression levels in AML patient samples versus normal hematopoietic cells.

Main Results:

• * TIP60 directly interacts with c-Myb, dependent on specific domains within both proteins.
• * TIP60 co-expression significantly reduces c-Myb's transcriptional activation capabilities.
• * TIP60 binds to the promoter of the c-Myc gene in a c-Myb-dependent manner.
• * Knockdown of TIP60 leads to increased expression of endogenous c-Myc.
• * c-Myb associates with histone deacetylases (HDAC1 and HDAC2), which are known TIP60 interactors.
• * TIP60 expression is significantly lower (approximately 60%) in primary AML samples compared to normal hematopoietic cells.

Conclusions:

• * TIP60 acts as a negative regulator of c-Myb transcriptional activity in hematopoietic cells, likely by recruiting histone deacetylases.
• * Reduced TIP60 expression in AML suggests that TIP60 is a tumor suppressor in this context.
• * Dysregulation or mutation of TIP60 may contribute to the development of c-Myb-driven leukemias.