Plays a role in transcription-coupled histone modification. Required for methylation of 'Lys-4' of histone H3. Plays a role in regulation of transcription. Required for maximal induction of heat-shock genes. Plays a role in Notch signaling in the wing margins. Interacts with the RNA polymerase II complex. May interact with the PAF1 complex. Co-localizes with Paf1 and RNA polymerase II on transcriptionally active sites on chromosomes. Detected in embryo. Expression is very low in larvae, pupae or adults. Death at pupal stage. Weaker mutants that live to adulthood exhibit reduced wing width.