Involved in ribosomal large subunit biogenesis. Binds the approximately 50 base pairs internal control region (ICR) of 5S ribosomal RNA genes. It is required for their RNA polymerase III-dependent transcription and may also maintain the transcription of other genes (PubMed:24120868). Also binds the transcribed 5S RNA's (By similarity). Ubiquitous. It is uncertain whether Met-1 is the initiator. Based on the lack of an in-frame AUG codon, mammalian TFIIIA may be translated from this non-AUG initiation site, which has a good Kozak context and which is well conserved among mammals. Extended N-terminus.