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). {ECO:0000250|UniProtKB:P17842, ECO:0000269|PubMed:24120868}. This is the function of Ensembl gene identifier ENSG00000122034 (GTF3A, general transcription factor IIIA).