Regulation of pri-miRNA processing by the hnRNP-like protein AtGRP7 in Arabidopsis.
Bottom Line: AtGRP7 overexpression caused a significant reduction in the level of 30 miRNAs and an increase for 14 miRNAs with a minimum log2 fold change of ± 0.5.Mutation of an arginine in the RNA recognition motif abrogated in vivo binding and the effect on miRNA and pri-miRNA levels, indicating that AtGRP7 inhibits processing of these pri-miRNAs by direct binding.Thus, AtGRP7 is an hnRNP-like protein with a role in processing of pri-miRNAs in addition to its role in pre-mRNA splicing.
Affiliation: Molecular Cell Physiology, Bielefeld University.Show MeSH
Mentions: AtGRP7 overexpression leads to reduced levels of miR172b and miR172b* with a concomitant increase in pri-miR172b which contains introns both 5′ and 3′ of the stem–loop structure (Figure 6A). Because splicing of introns located 3′ of the stem–loop can impact accumulation of mature miRNAs (73,74), we asked whether AtGRP7 affects splicing of pri-miR172b. In wt plants, some pri-miR172b retaining the intron was detected in addition to the spliced form. In AtGRP7-ox plants, the spliced pri-miR172b accumulated at the expense of the intron retained form, indicating that AtGRP7 indeed affects splicing of pri-miRNAs (Figure 6B and C). In contrast, splicing of the introns located upstream of the hairpin was not altered (not shown). Thus, an enhanced assembly of the spliceosome at the 5′end of the downstream intron in AtGRP7-ox plants may interfere with pri-miRNA processing. Alternatively, a slower release of miR172b and miR172b* caused by AtGRP7 binding may allow more efficient assembly of the spliceosome.