K92 Lactylation of YBX1 orchestrates m5C RNA recognition to facilitate colorectal Cancer progression

RNA 5-methylcytosine (m5C) methylation is a vital epitranscriptomic mark involved in regulating numerous cellular and disease processes. A central effector of m5C-modified transcripts is Y-box binding protein 1 (YBX1), a key RNA-binding factor that modulates multiple aspects of RNA metabolism. Here, we identify lysine 92 (K92) as a predominant and previously unrecognized site of lactylation on YBX1, installed by the acyltransferase p300 and erased by the delactylase SIRT2. Although K92 lactylation has little effect on YBX1's cellular localization or stability, it significantly promotes its ability to associate with m5C-modified transcripts. Further analysis reveals that the RNA-binding protein G3BP2 preferentially interacts with lactylated YBX1, facilitating its engagement with m5C-modified RNAs. This interaction proves functionally critical, as K92 lactylation is required for YBX1-driven malignant behaviors in colorectal cancer (CRC). Clinically, analysis of a small set of CRC specimens suggests elevated YBX1 lactylation, consistent with its potential pathological relevance. Together, these results uncover a lactylation-dependent mechanism that governs m5C RNA recognition and contributes to YBX1's oncogenic activity.