Rous sarcoma virus DR posttranscriptional elements use a novel RNA export pathway

Area of Science:

• Molecular Biology
• Virology
• Cell Biology

Background:

• Rous sarcoma virus (RSV) must export unspliced RNA to the cytoplasm, bypassing host cell restrictions.
• This process is crucial for viral replication and involves cis-acting direct repeat (DR) elements flanking the src gene.

Purpose of the Study:

• To investigate the mechanism of nuclear export of unspliced viral RNA by RSV.
• To determine if the RSV DR element functions as a constitutive transport element (CTE).
• To compare the RSV RNA export pathway with those of other retroviruses like HIV-1 and simian retroviruses.

Main Methods:

• Utilized a reporter construct to assess the function of the DR element in nuclear export.
• Investigated the involvement of CRM1 and Tap export proteins in the DR-mediated export pathway.
• Employed leptomycin B to test CRM1 dependency.

Main Results:

• The RSV DR element mediates the export of reporter constructs from the nucleus, functioning as a CTE.
• DR-mediated RNA export is independent of CRM1, distinguishing it from HIV-1's Rev/Rex pathway.
• RSV DR RNA did not bind to the Tap export protein, unlike simian retroviruses.

Conclusions:

• RSV utilizes a distinct nucleocytoplasmic export pathway for its unspliced RNA.
• This pathway is novel and differs from those employed by HIV-1 and simian retroviruses.
• The RSV DR element represents a unique mechanism for viral RNA nuclear export.