Notch signaling modulates the developmental program of multiple cell types. The cleaved intracellular region of the receptor possess the functional domain which influences T cell activation, proliferation and differentiation. However, in naïve CD4 T cells the mechanistic details underlying cleavage of Notch1 is not clearly understood. Notch functions by acting as a signaling hub and interacting with its canonical (CSL) and non-canonical (NFkB, mTOR, Akt) binding partners to cross-talk with other signaling pathways. Notch signaling drives the differentiation program of multiple T helper cell subsets (Th1, Th2, Th17, Th9, iTreg and TFH). Recent discoveries also demonstrated a role for microRNAs in T helper cell differentiation, particularly in Th1 cells. The miR-29 family of microRNAs limit Th1 differentiation by directly targeting the signature molecules of Th1 cells, ifng and tbx21. The post translational modifications of Notch1 during activation and differentiation of CD4 T cells are described here. We specifically demonstrate that Notch1 is constitutively cleaved in naïve cells and it is hyper-phosphorylated. Phosphorylation status of Notch1 changes upon TCR mediated activation, probably through dephosphorylation, resulting in different forms of phosphorylated Notch1. In Chapter 3, we study Notch1-mediated regulation of miR-29. We show that Notch1 suppresses miR-29 through CSL-dependent, canonical Notch signaling. Thus, our data indicate a novel mechanism for regulating miR-29 transcription in addition to STAT1 and NFkB. We demonstrated that Notch1 and IFNg act in an opposing manner to regulate the expression of miR-29, therefore modulating Th1 response.