CD8+ cytotoxic T lymphocytes (CTLs) play a crucial role in immune control and clearance of intracellular infections and tumours. Upon activation, naïve CTLs differentiate, resulting in the acquisition of lineage specific effector functions that includes the ability to kill virally infected cells via the secretion of the cytotoxic molecules perforin (PFP) and granzymes A and B (GZMA and GZMB) (1). While several studies have focused on the molecular regulation of PFP and GZMB expression (2,3), little is known of GZMA regulation. In vitro activation of naïve CD8+ T cells, in the presence of IL-4, enhanced STAT6 dependent GZMA expression, was associated with GATA3 binding and enrichment of transcriptionally permissive histone marks across the Gzma gene locus. Interestingly, while GZMA expression by effector influenza A virus-specific CTL directly ex vivo was associated with a similar permissive epigenetic signature, and GATA3 recruitment at the Gzma locus, this was independent of STAT6 mediated signaling. Given that GATA3 is key for CTL differentiation in response to infection (4), we hypothesized that GATA3 expression may be regulated by a distinct, IL4 independent signaling pathway. To explore this, we in vitro stimulated naïve CTLs in the presence of the NOTCH ligand Delta1 and showed that GZMA and GATA3 expression was upregulated when compared to CTLs activated in the absence of NOTCH signals. We propose that NOTCH signals received during CTL expansion in response to infection could potentially increase GATA3 expression and binding to the Gzma locus that in turn promotes the acquisition of a transcriptionally permissive chromatin state. Overall, this study provides insights into the molecular mechanisms that control transcriptional changes during CD8+ T cell differentiation.