Programmed ribosomal frameshifting during PLEKHM2 mRNA decoding generates a constitutively active proteoform that...

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Programmed ribosomal frameshifting is a known mechanism, primarily in viruses, for altering protein synthesis.
• Conserved frameshifting events in nuclear-encoded genes are rare and often debated.
• The gene PLEKHM2 plays a role in cellular processes, but its full regulatory mechanisms are not completely understood.

Purpose of the Study:

• To investigate the phenomenon of programmed ribosomal frameshifting in the human gene PLEKHM2.
• To characterize the mechanism and functional significance of this frameshifting event.
• To determine the role of frameshifting in PLEKHM2's function and cellular localization.

Main Methods:

• Analysis of mRNA sequences and ribosome behavior during translation of PLEKHM2.
• Site-directed mutagenesis to identify the frameshifting signal.
• Cellular localization studies using microscopy.
• Functional assays in PLEKHM2-knockout cardiomyocytes.

Main Results:

• A +1 programmed ribosomal frameshifting event was identified in the human PLEKHM2 gene at the conserved UCC_UUU_CGG sequence.
• The frameshift generates a novel C-terminal domain that forms an alpha-helix, relieving autoinhibition of PLEKHM2.
• Frameshifted PLEKHM2 associates with kinesin-1 for transport to cellular tips, independent of ARL8.
• Restoration of both canonical and frameshifted PLEKHM2 proteins is required to rescue contractile function in knockout cardiomyocytes.

Conclusions:

• Programmed ribosomal frameshifting is essential for PLEKHM2 function and normal cardiac activity.
• This finding expands the known repertoire of frameshifting mechanisms in nuclear-encoded genes.
• The frameshift-dependent regulation of PLEKHM2 impacts its localization and cellular function, particularly in cardiomyocytes.