bims-micpro Biomed News
on Discovery and characterization of microproteins
Issue of 2024–08–04
two papers selected by
Thomas Farid Martínez, University of California, Irvine
  1. Leaky ribosomal scanning enables tunable translation of bicistronic ORFs in green algae.
  2. Effect of Humanin and MOTS-c on ameliorating reproductive damage induced by prepubertal cyclophosphamide chemotherapy in male mice.
  1. bioRxiv. 2024 Jul 25. pii: 2024.07.24.605010. [Epub ahead of print]
    Leaky ribosomal scanning enables tunable translation of bicistronic ORFs in green algae.
    Marco A Duenas, Rory J Craig, Sean D Gallaher, Jeffrey L Moseley, Sabeeha S Merchant.
      Advances in sequencing technology have unveiled examples of nucleus-encoded polycistronic genes, once considered rare. Exclusively polycistronic transcripts are prevalent in green algae, although the mechanism by which multiple polypeptides are translated from a single transcript is unknown. Here, we used bioinformatic and in vivo mutational analyses to evaluate competing mechanistic models for polycistronic expression in green algae. High-confidence manually curated datasets of bicistronic loci from two divergent green algae, Chlamydomonas reinhardtii and Auxenochlorella protothecoides , revealed 1) a preference for weak Kozak-like sequences for ORF 1 and 2) an underrepresentation of potential initiation codons before ORF 2, which are suitable conditions for leaky scanning to allow ORF 2 translation. We used mutational analysis in Auxenochlorella protothecoides to test the mechanism. In vivo manipulation of the ORF 1 Kozak-like sequence and start codon altered reporter expression at ORF 2, with a weaker Kozak-like sequence enhancing expression and a stronger one diminishing it. A synthetic bicistronic dual reporter demonstrated inversely adjustable activity of green fluorescent protein expressed from ORF 1 and luciferase from ORF 2, depending on the strength of the ORF 1 Kozak-like sequence. Our findings demonstrate that translation of multiple ORFs in green algal bicistronic transcripts is consistent with episodic leaky ribosome scanning of ORF 1 to allow translation at ORF 2. This work has implications for the potential functionality of upstream open reading frames found across eukaryotic genomes and for transgene expression in synthetic biology applications.
    Significance Statement: Textbook dogma states that nucleus-encoded genes are monocistronic, producing transcripts with a single translated open reading frame. However, highly conserved bicistronic loci are pervasive in green algae that are separated by several hundred million years of evolution, speaking to their ancestral origins and functions within the Chlorophyte lineage. A combination of bioinformatic analysis and in vivo gene manipulation supports leaky ribosomal scanning as the primary mechanism for translation of multiple ORFs from bicistronic transcripts. We have successfully tuned synthesis levels of two proteins encoded on one mRNA by modifying the ORF 1 Kozak-like sequence. These findings may have broad applications in synthetic biology.
    DOI:  https://doi.org/10.1101/2024.07.24.605010
  2. Reprod Toxicol. 2024 Jul 28. pii: S0890-6238(24)00141-2. [Epub ahead of print] 108674
    Effect of Humanin and MOTS-c on ameliorating reproductive damage induced by prepubertal cyclophosphamide chemotherapy in male mice.
    Jinyuan Wang, Wen Wen, Liu Liu, Junhui He, Renhe Deng, Mingxuan Su, Shuhua Zhao, Huawei Wang, Meng Rao, Li Tang.
      Male patients who undergo prepubertal chemotherapy face the dual problems of fertility preservation in adulthood, including low testosterone, hypersexual function, and infertility. Humanin, as a small polypeptide coded within the mitochondrial DNA, with the mitochondrial short open reading frame named MOTS-c, both was believed to regulate mitochondrial homeostasis, be anti-inflammatory, improve metabolism, anti-apoptosis, and multiple pharmacological effects. However, there exists little evidence that reported Humanin and MOTS-c 's effects on moderating male spermatogenic function of patients after prepubertal chemotherapy. Here, we found that in vivo, mitochondrial polypeptides Humanin analog (HNG) and MOTS-c efficaciously protected the testicular spermatogenic function from reproductive injury. Moreover, transcriptomic sequencing analysis was performed to verify the differentially expressed genes such as Piwil2, AGT (angiotensinogen), and PTGDS (glycoprotein prostaglandin D2 synthase), which are related to the regulation of male reproductive function of male mice induced by prepubertal chemotherapy. Collectively, our data revealed that both Humanin analogs HNG and MOTS-c are the feasible approaches attached to the protective effect on the male reproductive function damaged by prepubertal chemotherapy.
    Keywords:  HNG; Humanin; MOTS-c; Male reproductive injury; Prepubertal chemotherapy
    DOI:  https://doi.org/10.1016/j.reprotox.2024.108674
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