Multiple RNA binding protein complexes interact with the rice prolamine RNA cis-localization zipcode sequences.

Area of Science:

• Plant Molecular Biology
• RNA Biology
• Seed Development

Background:

• Storage protein RNAs in rice seeds utilize zipcode sequences for localization.
• Specific RNA binding proteins (RBPs) interact with these zipcode sequences to mediate RNA transport.

Purpose of the Study:

• To investigate the binding interactions of five specific RBPs (RBP-A, RBP-I, RBP-J, RBP-K, RBP-Q) with prolamine zipcode sequences.
• To elucidate the assembly of multiprotein complexes and RNA-protein assemblies involved in storage protein RNA transport.

Main Methods:

• Coimmunoprecipitation-immunoblot analyses were performed.
• Experiments were conducted in the presence and absence of ribonuclease to study RNA-protein interactions.

Main Results:

• Five RBPs, belonging to the heterogeneous nuclear ribonucleoprotein class, specifically bind to zipcode RNA regions.
• These RBPs assemble into three multiprotein complexes, forming at least two distinct zipcode RNA-protein assemblies.
• One cytoplasmic assembly involves RBP-J and RBP-K forming a core with either RBP-A or RBP-I.
• A second, potentially nuclear, assembly includes RBP-Q and modified forms of other complexes.

Conclusions:

• Prolamine RNA transport is initiated in the nucleus with the formation of a zipcode-protein assembly.
• This assembly undergoes remodeling in the cytoplasm to ensure precise targeting of RNA to the cortical endoplasmic reticulum.