Specifically recognizes and binds N6-methyladenosine (m6A)-containing mRNAs, and regulates their stability (PubMed:30401835, PubMed:32943573). M6A is a modification present at internal sites of mRNAs and some non-coding RNAs and plays a role in mRNA stability and processing (PubMed:30401835, PubMed:32943573). Acts as a regulator of mRNA stability by promoting degradation of m6A-containing mRNAs via interaction with the CCR4-NOT complex (By similarity). The YTHDF paralogs (YTHDF1, YTHDF2 and YTHDF3) share m6A-containing mRNAs targets and act redundantly to mediate mRNA degradation and cellular differentiation (PubMed:32943573). Required to facilitate learning and memory formation in the hippocampus by binding to m6A-containing neuronal mRNAs (PubMed:30401835). Acts as a regulator of axon guidance by binding to m6A-containing ROBO3 transcripts (PubMed:30843071). Acts as a negative regulator of antigen cross-presentation in myeloid dendritic cells (PubMed:30728504). In the context of tumorigenesis, negative regulation of antigen cross-presentation limits the anti-tumor response by reducing efficiency of tumor-antigen cross-presentation (PubMed:30728504). Promotes formation of phase-separated membraneless compartments, such as P-bodies or stress granules, by undergoing liquid-liquid phase separation upon binding to mRNAs containing multiple m6A-modified residues: polymethylated mRNAs act as a multivalent scaffold for the binding of YTHDF proteins, juxtaposing their disordered regions and thereby leading to phase separation (By similarity). The resulting mRNA-YTHDF complexes then partition into different endogenous phase-separated membraneless compartments, such as P-bodies, stress granules or neuronal RNA granules (By similarity). Interacts with CNOT1; promoting recruitment of the CCR4-NOT complex (By similarity). Interacts with ribosomes (By similarity). Interacts with eIF3 (EIF3A or EIF3B). Interacts with YTHDF3 (By similarity). In brain, preferentially expressed in the hippocampus. The disordered regions have the ability to interact with each other and to 'phase separate' into liquid droplets within the cytosol following binding to mRNAs containing multiple m6A-modified residues. This leads to the partition of m6A-containing mRNAs into membraneless compartments, where mRNAs may be stored, degraded or used to transport mRNAs to dendritic arbors in neurons. Mice are viable and were born at the expected Mendelian ratio (PubMed:32943573). They however display learning and memory defects (PubMed:30401835). Mice develop normally up to four months of age and have normal gross hippocampal histology (PubMed:30401835). They however show learning and memory defects as well as impaired hippocampal synaptic transmission and long-term potentiation (PubMed:30401835). Hippocampal CA1 neurons show reduced dendritic spine density but unaltered spine size (PubMed:30401835). Conditional deletion in spinal commissural neurons results in pre-crossing axon guidance defects (PubMed:30843071). Knockout mice show an improved tumor control associated with increased infiltration of the tumor by T-cells, due to elevated antigen-specific CD8(+) T-cell anti-tumor response (PubMed:30728504). Conditional deletion in myeloid dendritic cells causes increased cross-presentation of tumor antigens and the cross-priming of CD8(+) T-cells (PubMed:30728504). Mice lacking Ythdf1, Ythdf2 and Ythdf3 display early embryonic lethality and show defects in embryonic stem cell differentiation (PubMed:32943573). Belongs to the YTHDF family. YTHDF1 subfamily. Was initially reported to act as a regulator of mRNA translation efficiency by promoting ribosome loading to m6A-containing mRNAs and by interacting with translation initiation factors eIF3 (EIF3A or EIF3B), thereby facilitating translation initiation (PubMed:30401835, PubMed:30728504, PubMed:30843071). These studies suggested that the 3 different paralogs (YTHDF1, YTHDF2 and YTHDF3) have unique functions with limited redundancy (PubMed:30401835, PubMed:30728504, PubMed:30843071). However, later studies showed that YTHDF1, YTHDF2 and YTHDF3 paralogs have redundant functions to a profound extent and directly promote degradation of m6A-containing mRNAs (PubMed:32943573). The effect on translation efficiency observed earlier is probably indirect (PubMed:32943573).