Tubulin acetylation: A novel functional avenue for CDYL in sperm

Motility in sperm is driven by the flagella, the principal component of which is the axoneme. The microtubules which make up the 9 + 2 axoneme are composed of heterodimers of alpha and beta tubulins and undergo several post-translational modifications. We have earlier reported that HDAC6 functions as tubulin deacetylase in sperm and has a role in sperm movement. While exploring the specific tubulin acetyltransferase (TAT) in sperm, we observed the presence of Chromodomain Y-Like (CDYL), on the principal piece of rat spermatozoa which compelled us to explore its function in sperm. CDYL was observed to be colocalized with acetylated alpha-tubulin (Ac α Tubulin) in sperm flagella. Sperm axonemal fraction showed the presence of CDYL protein indicating its strong association with flagellar microtubules. Sequence alignment of CDYL chromo domain and Alpha tubulin acetyltransferase (αTAT1) revealed that of the 10 residues of αTAT1 known to be involved in α-tubulin binding, 5 residues were identical and 1 was conserved between the two proteins. Docking of CDYL chromo domain and α-tubulin showed that 6 of the 11 important binding residues of α-tubulin showed an interaction with CDYL chromo domain. The putative CDYL chromodomain -α-tubulin interaction was further confirmed by Microscale Thermophoresis. We further asserted the ability of recombinant CDYL and Sperm CDYL to acetylate soluble tubulin and microtubules in vitro. Acetylation of tubulin was increased over twofold in cells overexpressing CDYL. Thus, our studies convincingly demonstrate the ability of CDYL to moonlight as a tubulin acetyltransferase.