Multifunctional RNA Binding Protein OsTudor-SN in Storage Protein mRNA Transport and Localization

Abstract

The multifunctional RNA-binding protein Tudor-SN plays multiple roles in transcriptional and posttranscriptional processes due to its modular domain structure, consisting of four tandem Staphylococcus nuclease (SN)-like domains (4SN), followed by a carboxyl-terminal Tudor domain, followed by a fifth partial SN sequence (Tsn). In plants, it confers stress tolerance, is a component of stress granules and P-bodies, and may participate in stabilizing and localizing RNAs to specific subdomains of the cortical-endoplasmic reticulum in developing rice (Oryza sativa) endosperm. Here, we show that, in addition to the intact rice OsTudor-SN protein, the 4SN and Tsn modules exist as independent polypeptides, which collectively may coassemble to form a complex population of homodimer and heteroduplex species. The 4SN and Tsn modules exhibit different roles in RNA binding and as a protein scaffold for stress-associated proteins and RNA-binding proteins. Despite their distinct individual properties, mutations in both the 4SN and Tsn modules mislocalize storage protein mRNAs to the cortical endoplasmic reticulum. These results indicate that the two modular peptide regions of OsTudor-SN confer different cellular properties but cooperate in mRNA localization, a process linking its multiple functions in the nucleus and cytoplasm.mRNA localization is readily evident in structurally polarized somatic cells

RNA-Binding Protein RBP-P Is Required for Glutelin and Prolamine mRNA Localization in Rice Endosperm Cells

“…One is OsTudor-SN (Sami-Subbu et al, 2001;Okita and Choi, 2002;Wang et al, 2008), previously called Rp120, which consists of four tandem staphylococcus nuclease (SN)-like domains (4SN module) followed by a C-terminal region containing a Tudor domain and truncated SN (TSN module). Mutations of OsTudor-SN resulted in mislocalization of both prolamine and glutelin mRNAs (Chou et al, 2017). While the 4SN module exhibits RNA binding activity, the TSN module binds to multiple RNA binding proteins.…”

“…While the 4SN module exhibits RNA binding activity, the TSN module binds to multiple RNA binding proteins. The two independent modules likely cooperate in mRNA localization (Chou et al, 2017).…”

mRNA Localization in Plant Cells

“…The interrelatedness of the three RNA transport pathways suggests that they share common trans-factors for targeting to the ER membrane, while glutelin and prolamine pathways require additional factors for selective transport (Chou et al, 2019). Indeed, our studies showed that prolamine and glutelin zipcode sequences bind identical transfactors, Tudor-SN (Chou et al, 2017;Tian et al, 2018, 2019), RBP-P (Chou et al, 2017; Tian et al, 2018, 2019), and RBP-L (Chou et al, 2017;Tian et al, 2018Tian et al, , 2019.…”

“…This RBP was initially identified as a cytoplasm-localized, cytoskeleton-associated protein in developing rice grains (Sami-Subbu et al, 2001;Wang et al, 2008). It contains four tandem Staphylococcus nuclease domains (4SN module) and a Tudor domain followed by an additional truncated SN domain in the C terminus (Tsn module; Chou et al, 2017). The N-terminal 4SN module directly binds to glutelin and prolamine mRNAs, while the Tsn module possesses the capacity to interact with eight other RBPs (Chou et al, 2017).…”

“…It contains four tandem Staphylococcus nuclease domains (4SN module) and a Tudor domain followed by an additional truncated SN domain in the C terminus (Tsn module; Chou et al, 2017). The N-terminal 4SN module directly binds to glutelin and prolamine mRNAs, while the Tsn module possesses the capacity to interact with eight other RBPs (Chou et al, 2017). These binding activities collectively contribute to the involvement of Tudor-SN in glutelin and prolamine mRNA localization (Wang et al, 2008;Chou et al, 2017), as reflected by the partial mislocalization of storage protein mRNAs in rice lines expressing Tudor-SN possessing mutations in the fourth SN and Tudor domains (Chou et al, 2017).…”