An early attempt to understand how the packing of DNA into c

An early attempt to understand how the packing of DNA into chromatin affects transcription in eukaryotes used a defined template, purified RNA polymerase II, and the general transcription factors – TFIIA, TFIIB, TFIID, and TFIIE. If the template was first assembled into nucleosomes, no transcription was detected when the transcription components were added (Fig. lane 2). If the template was preincubated with the transcription components (in the absence of NTPs), then assembled into chromatin and the chromatin template was purified, transcription proceeded just as well as it does on the naked DNA template when the transcription components were added (compare lanes 1 and 3). This suggested that the transcription components, when bound to the template, keep the promoter accessible. This phenomenon was investigated in more detail in two additional kinds of experiments. In one, individual components were omitted during the preincubation (lanes 4 to 8). In the second, individual components were omitted during the transcription assay (lanes 9 to 13).

A. Which of the transcription components must be present during the preincubation in order for the template to be active after chromatin assembly?

B. Which of the transcription components can form a complex with the template that is stable to chromatin formation and subsequent purification?

C. Which of the transcription components must be added during the transcription assay in order to produce a transcript?

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Solution

A)TFIIA must be present during the preincubation in order for the template to be active after chromatin assembly because it is basically defined as the nuclear protein which takes an important part involving in the RNA polymerase II-dependent transcription of DNA.Moreover it is one of several general transcription factors   which is required for all transcription events that use RNA polymerase II.This includes the preincubations events as well.

B)TFIID is the transcription component that can form a complex with the template that is stable to chromatin formation and subsequent purification because it makes the the RNA polymerase II preinitiation complex.In this process the RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II ,Moreoever this is next recruited to the promoters of protein-coding genes in living cells which is very important as part of chromatic formation.

C)TFIID AND TFIIE must be be added during the transcription assay in order to produce a transcript because TFIIE is very important and is   involved in DNA melting at the promoter.This means it forms the transcript by containing a zinc ribbon motif that can bind single stranded DNA.This zinc ribbon trancends from the TFIID.