Sequence and expression of transcripts of the human T-cell receptor beta-chain genes.

T lymphocytes can produce mRNAs from the first or second constant region of the T-cell antigen receptor beta-chain. A 1.3-kilobase (kb) transcript encoding the mature protein contains V, J and one of the two C region sequences, but does not always contain D sequences. A 1.0-kb mRNA, found mainly in immature T cells, does not contain V sequences and can result from transcription that initiates upstream from an unrearranged J element.