LIN-53 (Rbbp4/7 in mammals) is a histone chaperone that is part of several histone remodeling and modifying complexes (Eitoku, 2007; Loyola 2004). It has previously been identified as a barrier of reprogramming, as depletion of LIN-53 enables the direct conversion of germ cells into specific somatic cell types such as glutamatergic taste neurons in C. elegans (Tursun et al., 2011). Next to its role in reprogramming, LIN-53 plays a role in muscle maintenance and life span regulation in C. elegans, as
lin-53 mutants show motility defects, impairment of muscle structure and a decreased lifespan compared to WT controls. Interestingly, muscle-specific rescue of LIN-53 expression could save the muscle but not the aging phenotype (Muthel et al., in revision), indicating a distinct role of LIN-53 in specific tissues. Strikingly, transcriptome analysis (RNA-seq) of different
lin-53 mutant backgrounds revealed strong upregulation of core histone gene expression upon
lin-53 depletion. Under normal conditions, core histones are only highly expressed in S-phase, where they are necessary to pack the newly synthesized DNA. Interestingly, little to nothing is known about the transcriptional regulation of canonical histone genes. Therefore, we are investigating the mechanisms underlying this de-repression of histone gene expression and its physiological consequences in
lin-53-depleted animals. To elucidate the distinct role of LIN-53 in specific tissues, CRISPR/Cas9-mediated gene editing was used to tag the endogenous
lin-53 locus with the auxin-inducible degron (AID) (Zhang et al., 2015) in order to knock down LIN-53 in a tissue specific manner. Furthermore, to identify tissue-specific protein interactions as well as DNA binding of LIN-53, we are using the in vivo biotinylation approach based on the BirA enzyme (Waaijers et al., 2016). The tissue-specific in-depth analysis of LIN-53 may reveal unprecedented insights into how histone gene expression is regulated.