GRSF-1: a poly(A)+ mRNA binding protein which interacts with a conserved G-rich element

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• A specific 14-base G-rich RNA element was identified in numerous mRNAs.
• Previous identification of a nuclear protein, DSEF-1, that interacts with this G-rich element.

Purpose of the Study:

• To identify and characterize cellular proteins that bind to the G-rich RNA element.
• To differentiate novel G-rich RNA binding proteins from previously identified ones.

Main Methods:

• Screening of a HeLa cell cDNA library using the G-rich RNA element as a probe.
• Characterization of the identified protein (GRSF-1) using techniques like Western blot, peptide mapping, and indirect immunofluorescence microscopy.
• In vivo UV cross-linking to confirm RNA binding in living cells.

Main Results:

• A novel cellular protein, GRSF-1, was identified and found to bind RNAs containing the G-rich element.
• GRSF-1 was distinguished from the nuclear protein DSEF-1 based on molecular weight, peptide maps, and antibody cross-reactivity.
• GRSF-1 was localized to the cytoplasm and shown to bind poly(A)+ mRNA in living human cells.
• Western blot analysis revealed four cytoplasmic proteins expressing GRSF-1 specific epitopes.
• GRSF-1 possesses three potential RNA recognition motifs and two auxiliary domains, similar to other RNA-binding proteins.

Conclusions:

• GRSF-1 is a distinct cytoplasmic RNA-binding protein that interacts with G-rich elements in mRNAs.
• The protein's domain organization suggests conserved mechanisms for RNA binding across different proteins.
• GRSF-1 is involved in binding messenger RNA in the cytoplasm of human cells.