The Hepatitis B virus PREalpha (HBV PREalpha) is an RNA structure that is shown to play a role in nuclear export of HBV mRNAs.
HBV PREalpha consists of a 30 nt stem-loop, with a 5 nt apical loop. The conserved stem-loop was predicted within the HBV PRE sequence and confirmed by mutagenesis. The Rfam structure is based on a covariation model and is consistent with its solution structure.
The exact role of this structure in nuclear export has not yet been determined
References
Hepatitis B virus PRE alpha Wikipedia(Text) CC BY-SA