Human NFX1 protein was identified as a protein that represses class II MHC (major histocompatibility complex) gene expression. NFX1 binds a conserved cis-acting element, termed the X-box, in promoters of human class II MHC genes. The Cys-rich region contains several NFX1-type zinc finger domains. Frequently, a R3H domain is present in the C-terminus, and a RING finger domain and a PAM2 motif are present in the N-terminus. The lack of R3H and PAM2 motifs in the plant proteins indicates functional differences. Plant NFX1-like proteins are proposed to modulate growth and survival by coordinating reactive oxygen species, salicylic acid, further biotic stress and abscisic acid responses. A common feature of all members may be E3 ubiquitin ligase, due to the presence of a RING finger domain, as well as DNA binding. NFX1 is a member of the DEAD-like helicase superfamily, a diverse family of proteins involved in ATP-dependent RNA or DNA unwinding. This domain contains the ATP-binding region.
Jiyao W et al.(2023). "The conserved domain database in 2023.",