Chromodomains are found in many regulators of chromatin structure, and most of 
them recognize methylated lysines on histones. Here, we investigate the role of 
the Drosophila melanogaster protein Corto's chromodomain. The Enhancer of 
Trithorax and Polycomb Corto is involved in both silencing and activation of 
gene expression. Over-expression of the Corto chromodomain (CortoCD) in 
transgenic flies shows that it is a chromatin-targeting module, critical for 
Corto function. Unexpectedly, mass spectrometry analysis reveals that 
polypeptides pulled down by CortoCD from nuclear extracts correspond to 
ribosomal proteins. Furthermore, real-time interaction analyses demonstrate that 
CortoCD binds with high affinity RPL12 tri-methylated on lysine 3. Corto and 
RPL12 co-localize with active epigenetic marks on polytene chromosomes, 
suggesting that both are involved in fine-tuning transcription of genes in open 
chromatin. RNA-seq based transcriptomes of wing imaginal discs over-expressing 
either CortoCD or RPL12 reveal that both factors deregulate large sets of common 
genes, which are enriched in heat-response and ribosomal protein genes, 
suggesting that they could be implicated in dynamic coordination of ribosome 
biogenesis. Chromatin immunoprecipitation experiments show that Corto and RPL12 
bind hsp70 and are similarly recruited on gene body after heat shock. Hence, 
Corto and RPL12 could be involved together in regulation of gene transcription. 
We discuss whether pseudo-ribosomal complexes composed of various ribosomal 
proteins might participate in regulation of gene expression in connection with 
chromatin regulators.