FAETL motif required for leukemic transformation by v-Myb

Area of Science:

• Molecular Biology
• Oncology
• Virology

Background:

• The avian myeloblastosis virus (AMV) v-Myb protein is a nuclear oncoprotein capable of inducing leukemia and transforming myeloid cells.
• Previous studies identified a C-terminal domain (amino acids 296-371) essential for v-Myb's transcriptional activation and transforming capabilities.

Purpose of the Study:

• To further investigate the functional significance of the C-terminal domain of v-Myb.
• To precisely define the minimal region required for transcriptional activation and oncogenic transformation by v-Myb.

Main Methods:

• Analysis of a series of C-terminal v-Myb mutants.
• Deletion analyses to identify essential amino acid subregions.
• Investigation of the role of putative leucine zipper and phosphorylation sites.
• Study of GAL4-Myb fusions to assess protein conformation.

Main Results:

• A strong correlation exists between transcriptional activation and leukemic transformation in v-Myb mutants.
• A 10-amino-acid subregion, termed the "FAETL" motif (amino acids 321-330), was identified as essential for v-Myb function.
• The FAETL motif's function is independent of an intact leucine zipper structure or adjacent phosphorylation sites.
• This region is crucial for maintaining a fully functional v-Myb conformation.

Conclusions:

• The FAETL motif is a critical determinant of v-Myb's oncogenic activity.
• v-Myb's essential C-terminal region functions differently from c-Myb's proposed inhibitory leucine zipper.
• The FAETL motif is essential for v-Myb's function without relying on a heptad leucine repeat.