Poster abstracts

Poster number 54 submitted by Benjamin Pastore

Pre-piRNA trimming prevents piRNAs from being erroneously targets by RNA dependent RNA polymerase

Benjamin Pastore (Department of Biological Chemistry and Pharmacology, The Center for RNA Biology, The Ohio State Biochemistry Program, The Ohio State University), Hannah L. Hertz (Department of Biological Chemistry and Pharmacology, The Center for RNA Biology, The Ohio State University), Wen Tang (Department of Biological Chemistry and Pharmacology, The Center for RNA Biology, The Ohio State Biochemistry Program, The Ohio State University)

Abstract:
In the germlines of animals the PIWI interacting (pi)RNA pathway suppresses the expression of transposable elements, thereby maintaining genome integrity and fertility. Following transcription from discrete genomic loci, piRNAs undergo two evolutionarily conserved 3’ end processing steps to complete maturation. In the first, 22-33 nucleotide (nt) long pre-piRNAs are trimmed to their mature length of 21 nt by the 3' to 5' exonuclease PARN-1. Following PARN-1 trimming, piRNAs are 2'-O methylated at their 3' termini by the methyltransferase HENN-1. It is well known that loss of PARN-1 and/or HENN-1 result in piRNA destabilization, however, other consequences of improper piRNA maturation remain unknown. In this unpublished work, we report that upon loss of PARN-1, antisense piRNA sequences accumulate in the germlines of C. elegans nematodes. We find that long untrimmed pre-piRNAs serve as templates for antisense piRNA generation, and that the RNA Dependent RNA Polymerase (RdRP) components EGO-1 and EKL-1 are responsible for synthesizing antisense piRNA sequences. In all this work identifies and characterizes a new species of small RNA in C. elegans, as well as defines a previously unknown consequence of pre-piRNA misprocessing.

References:
Pastore, B., Hertz, H.L., Price, I.F., and Tang, W. (2021). pre-piRNA trimming and 2'-O-methylation protect piRNAs from 3' tailing and degradation in C. elegans. Cell Rep 36, 109640.
Gainetdinov, I., Colpan, C., Cecchini, K., Arif, A., Jouravleva, K., Albosta, P., Vega-Badillo, J., Lee, Y., Ozata, D.M., and Zamore, P.D. (2021). Terminal modification, sequence, length, and PIWI-protein identity determine piRNA stability. Mol Cell 81, 4826-4842 e4828.
Ozata, D.M., Gainetdinov, I., Zoch, A., O'Carroll, D., and Zamore, P.D. (2019). PIWI-interacting RNAs: small RNAs with big functions. Nature Reviews Genetics 20, 89-108.
Tang, W., Tu, S., Lee, H.C., Weng, Z., and Mello, C.C. (2016). The RNase PARN-1 Trims piRNA 3' Ends to Promote Transcriptome Surveillance in C. elegans. Cell 164, 974-984.

Keywords: piRNA, small RNA, C elegans