A B1 SINE element within the mouse Malat1 long noncoding RNA acts as an internal ribosome entry site mediating micropeptide translation.

A B1 SINE element within mouse Malat1 acts as an IRES that enables cap-independent translation of the M1 micropeptide in neurons.

• Why it matters: Understanding how noncoding RNAs like Malat1 can produce functional peptides challenges the traditional view of their roles and may reveal new mechanisms of gene regulation in cells.
• What they did: The researchers used in vivo chemical probing, structural modeling, and affinity purification to identify a three-stem-loop IRES structure overlapping a B1 SINE element that binds ribosomal and translation factors, and they showed that depletion of specific cofactors inhibits M1 translation.
• The result: This work uncovers a hidden functional unit within Malat1 that facilitates micropeptide production, suggesting that some long noncoding RNAs may have coding potential through embedded IRES elements.