RAMAC (RNA guanine-7 methyltransferase activating subunit), also known as RAM (RNMT-Activating Mini protein) or Fam103a1, is an essential regulatory subunit of the mammalian mRNA cap methyltransferase complex 1. RAMAC functions as an obligate component that activates RNMT (RNA guanine-7 methyltransferase), the enzyme responsible for methylating the N7 position of the 7-methylguanosine cap structure on mRNAs 1. The protein consists of an N-terminal RNMT-activating domain and a C-terminal RNA-binding domain 1. RAMAC enhances the recruitment of the methyl donor S-adenosyl-L-methionine to RNMT through allosteric mechanisms, binding to a positively charged surface groove on RNMT that stabilizes critical structural elements for optimal enzyme activity 2. Beyond its role in cap methylation, RAMAC promotes RNA polymerase II-dependent transcription independent of its cap methyltransferase activity, interacting with nascent transcripts and transcription factors to stimulate overall transcriptional output 3. Nuclear localization of RAMAC requires PY nuclear localization signals and depends on Kapβ2-mediated nuclear import 4. RAMAC is essential for maintaining mRNA expression levels, protein translation, and cell viability, making it a critical component of the gene expression machinery 1.