Transcription factor that acts as a master regulator of lysosomal biogenesis and immune response. Specifically recognizes and binds E-box sequences; efficient DNA-binding requires dimerization with itself or with another MiT/TFE family member such as TFEB or MITF. Involved in the cellular response to amino acid availability by acting downstream of MTOR: in the presence of nutrients, TFE3 phosphorylation by MTOR promotes its cytosolic retention and subsequent inactivation. Upon starvation or lysosomal stress, inhibition of MTOR induces TFE3 dephosphorylation, resulting in nuclear localization and transcription factor activity .