Binding of LARP6 to the Conserved 5′ Stem-Loop Regulates Translation of mRNAs Encoding Type I Collagen

Le Cai, Dillon Fritz, Lela Stefanovic, Branko Stefanovic*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    84 Scopus citations

    Abstract

    Type I collagen is the most abundant protein in the human body, produced by folding of two α1(I) polypeptides and one α2(I) polypeptide into the triple helix. A conserved stem-loop structure is found in the 5′ untranslated region of collagen mRNAs, encompassing the translation start codon. We cloned La ribonucleoprotein domain family member 6 (LARP6) as the protein that binds the collagen 5′ stem-loop in a sequence-specific manner. LARP6 has a distinctive bipartite RNA binding domain not found in other members of the La superfamily. LARP6 interacts with the two single-stranded regions of the 5′ stem-loop. The Kd for binding of LARP6 to the 5′ stem-loop is 1.4 nM. LARP6 binds the 5′ stem-loop in both the nucleus and the cytoplasm. In the cytoplasm, LARP6 does not associate with polysomes; however, overexpression of LARP6 blocks ribosomal loading on collagen mRNAs. Knocking down LARP6 by small interfering RNA also decreased polysomal loading of collagen mRNAs, suggesting that it regulates translation. Collagen protein is synthesized at discrete regions of the endoplasmic reticulum. Using collagen-GFP (green fluorescent protein) reporter protein, we could reproduce this focal pattern of synthesis, but only when the reporter was encoded by mRNA with the 5′ stem-loop and in the presence of LARP6. When the reporter was encoded by mRNA without the 5′ stem-loop, or in the absence of LARP6, it accumulated diffusely throughout the endoplasmic reticulum. This indicates that LARP6 activity is needed for focal synthesis of collagen polypeptides. We postulate that the LARP6-dependent mechanism increases local concentration of collagen polypeptides for more efficient folding of the collagen heterotrimer.

    Original languageEnglish (US)
    Pages (from-to)309-326
    Number of pages18
    JournalJournal of molecular biology
    Volume395
    Issue number2
    DOIs
    StatePublished - Jan 15 2010

    Keywords

    • LARP6
    • RNA binding
    • translation
    • type I collagen

    ASJC Scopus subject areas

    • Biophysics
    • Structural Biology
    • Molecular Biology

    Fingerprint

    Dive into the research topics of 'Binding of LARP6 to the Conserved 5′ Stem-Loop Regulates Translation of mRNAs Encoding Type I Collagen'. Together they form a unique fingerprint.

    Cite this