Chromosomal transcription occurs through an intricate network of proteins (called the transcriptome, a complex molecular machinery involved in DNA transcription), in which the DNA polymerase alpha (Polα), delta polymerase (Polδ) and epsilon (Polε) proteins are lined up with proteins Additional – includes the proteins AND-1, CLASPIN, and TIMELESS-TIPIN (respectively defined in baking yeast Saccharomyces cerevisiae As Ctf4, Mrc1, and Tof1) – About the transcriptional helicase of CDC45, MCM and GINS (CMG) proteins. Since no efficient transcriptional body has been recombined from purified proteins, it is not yet clear how these elements contribute to human DNA transcription, and whether optimal DNA synthesis requires additional proteins.
In this published paper, the research team reports a biochemical recombination of a human transcriptome that achieves rapid and efficient DNA transcription by 11 purified human transcription factor proteins, consisting of 43 polypeptide amino acid chains. The team found that epsilon polymerase, in contrast to delta polymerase, is necessary for optimal synthesis of advanced DNA strands. Surprisingly, transcription of advanced strands by epsilon polymerase was highly dependent on the sliding block factor catalytic continuum DNA transcription (PCNA) and on the alternative mass loading complex CTF18–RFC.
The scientists also demonstrated how CLASPIN and TIMELESS-TIPIN contribute to transcriptional development, and showed that AND-1 directly enhances transcription of advanced strands, unlike in the baking yeast transcriptome. Furthermore, although AND-1 binds to the alpha polymerase primase, this interaction can be dispensed with for late transcription, which indicates that alpha polymerase is actively employed via an AND-1-independent mechanism to stimulate the human transcriptional body.
Altogether, this work reveals how the human transcriptome achieves rapid and efficient transcription of both forward and late strands of DNA, and is an efficient system worthy of study in research on the human transcriptome and its interactions with other DNA metabolism.
