TCEA1, also named as transcription elongation factor A protein 1, is a 301 amino acid protein, which contains 1 TFIIS central domain and belongs to the TFS-II family. TCEA1 localizes in the nucleus and is necessary for efficient RNA polymerase II transcription elongation past template-encoded arresting sites. The arresting sites in DNA have the property of trapping a certain fraction of elongating RNA polymerases that pass through, resulting in locked ternary complexes. Cleavage of the nascent transcript by S-II allows the resumption of elongation from the new 3'-terminus. The calcualted molecular weight of TCEA1 is 37 kDa, but modified TCEA1 is about 37-40 kDa.