The basic region/helix-loop-helix/leucine repeat transcription factor USF interferes with Ras transformation

Area of Science:

• Molecular Biology
• Cellular Biology
• Oncology

Background:

• Upstream stimulatory factor (USF) belongs to the basic helix-loop-helix/leucine repeat transcription factor family.
• USF shares DNA-binding sequences with the myc oncogene and its DNA-binding domain is structurally similar to Max.
• USF heterodimerizes with FIP/USF2, a factor interacting with Fos, implicating USF in cell proliferation pathways.

Purpose of the Study:

• To investigate the role of Upstream stimulatory factor (USF) in cellular growth control.
• To determine if USF acts as an oncogene or influences Ras-driven transformation.

Main Methods:

• Investigated USF's effect on Ras-driven transformation.
• Assessed the role of USF's transactivating and DNA-binding domains in this effect.
• Compared the inhibitory effect of full-length USF with its minimal DNA-binding domain.

Main Results:

• Upstream stimulatory factor (USF) does not function as an oncogene.
• USF actively interferes with Ras-driven cell transformation.
• This inhibitory effect is dependent on USF's DNA-binding activity but independent of its transactivating domains.
• The minimal USF DNA-binding domain alone did not inhibit, and slightly enhanced, Ras transformation.

Conclusions:

• Upstream stimulatory factor (USF) plays a significant role in controlling cell growth and proliferation.
• USF exerts its regulatory function through both promoter sequence binding and protein-protein interactions.
• USF's inhibitory influence on Ras transformation highlights its complex role beyond simple oncogenic potential.