5-Bromo-UTP (5-BrUTP) trisodium is an analog of uridine triphosphate (UTP). As an RNA synthesis precursor, 5-Bromo-UTP trisodium is incorporated into newly synthesized RNA strands during transcription, substituting for some UTP. This compound is useful for labeling newly formed RNA, enabling high-resolution visualization of transcription sites and RNA transport.