Functional Interaction between U1snRNP and Sam68 Insures Proper 3' End Pre-mRNA Processing during Germ Cell Differentiation

Cell Rep. 2019 Mar 12;26(11):2929-2941.e5. doi: 10.1016/j.celrep.2019.02.058.


Male germ cells express the widest repertoire of transcript variants in mammalian tissues. Nevertheless, factors and mechanisms underlying such pronounced diversity are largely unknown. The splicing regulator Sam68 is highly expressed in meiotic cells, and its ablation results in defective spermatogenesis. Herein, we uncover an extensive splicing program operated by Sam68 across meiosis, primarily characterized by alternative last exon (ALE) regulation in genes of functional relevance for spermatogenesis. Lack of Sam68 preferentially causes premature transcript termination at internal polyadenylation sites, a feature observed also upon depletion of the spliceosomal U1snRNP in somatic cells. Notably, Sam68-regulated ALEs are characterized by proximity between U1snRNP and Sam68 binding motifs. We demonstrate a physical association between Sam68 and U1snRNP and show that U1snRNP recruitment to Sam68-regulated ALEs is impaired in Sam68-/- germ cells. Thus, our study reveals an unexpected cooperation between Sam68 and U1snRNP that insures proper processing of transcripts essential for male fertility.

Keywords: Sam68; U1snRNP; alternative polyadenylation; alternative splicing; germ cell differentiation; male fertility; spermatogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions
  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • HEK293 Cells
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Protein Binding
  • RNA Splicing*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Ribonucleoproteins, Small Nuclear / genetics
  • Ribonucleoproteins, Small Nuclear / metabolism*
  • Spermatogenesis*
  • Spermatogonia / cytology
  • Spermatogonia / metabolism*
  • Transcription Termination, Genetic*


  • 3' Untranslated Regions
  • Adaptor Proteins, Signal Transducing
  • Khdrbs1 protein, mouse
  • RNA-Binding Proteins
  • Ribonucleoproteins, Small Nuclear