Held out wings RNA binding activity in the cytoplasm during early spermatogenesis

Area of Science:

• Molecular Biology
• Developmental Biology
• Genetics

Background:

• Held out wings (HOW) is an essential RNA-binding protein for spermatogenesis in Drosophila melanogaster.
• HOW belongs to the signal transduction and activation of RNA (STAR) protein family, regulating post-transcriptional gene expression.
• The RNA-binding characteristics of the short cytoplasmic isoform, HOW(S), were previously unknown.

Purpose of the Study:

• To investigate the RNA-binding properties of the HOW(S) isoform.
• To identify novel transcripts regulated by HOW(S) in germ stem cells and spermatogonia.
• To elucidate the role of HOW(S) in post-transcriptional gene regulation during spermatogenesis.

Main Methods:

• In vivo RIP-seq (RNA immunoprecipitation sequencing) was employed to identify HOW(S)-bound transcripts.
• Bioinformatic analysis was used to identify enriched RNA sequence motifs.
• mRNA binding affinity assays were performed for specific HOW(S)-RNA interactions.

Main Results:

• RIP-seq identified 121 novel transcripts bound by HOW(S) in germ stem cells and spermatogonia.
• Enriched motifs included (A/G/U)CUAAC in 3'-UTRs and GCG(A/U)G in 5'-UTRs.
• HOW(S) demonstrated high-affinity binding to CUAAC motifs in lola and hipk mRNAs, influencing mRNA stability and translation.

Conclusions:

• Cytoplasmic HOW(S) binds to CUAAC motifs in 3'-UTRs, impacting mRNA stability and translation.
• HOW(S) plays a crucial role in regulating gene expression during spermatogenesis through specific RNA interactions.
• This study offers new insights into STAR protein-RNA interactions and their functional significance in male germline development.