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Hyperphosphorylated C-terminal repeat domain-associating proteins in the nuclear proteome link transcription to
Sherry M Carty1, Arno L Greenleaf
1Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
Abstract:
Using an interaction blot approach to search in the human nuclear proteome, we identified eight novel proteins that bind the hyperphosphorylated C-terminal repeat domain (phosphoCTD) of RNA polymerase II. Unexpectedly, five of the new phosphoCTD-associating proteins (PCAPs) represent either enzymes that act on DNA and chromatin (topoisomerase I, DNA (cytosine-5) methyltransferase 1, poly(ADP-ribose) polymerase-1) or proteins known to bind DNA (heterogeneous nuclear ribonucleoprotein (hnRNP) U/SAF-A, hnRNP D). The other three PCAPs represent factors involved in pre-mRNA metabolism as anticipated (CA150, NSAP1/hnRNP Q, hnRNP R) (note that hnRNP U/SAF-A and hnRNP D are also implicated in pre-mRNA metabolism). Identifying as PCAPs proteins involved in diverse DNA transactions suggests that the range of phosphoCTD functions extends far beyond just transcription and RNA processing. In view of the activities possessed by the DNA-directed PCAPs, it is likely that the phosphoCTD plays important roles in genome integrity, epigenetic regulation, and potentially nuclear structure. We present a model in which the phosphoCTD association of the PCAPs poises them to act either on the nascent transcript or on the DNA/chromatin template. We propose that the phosphoCTD of elongating RNA polymerase II is a major organizer of nuclear functions.
Insights
Researchers discovered novel proteins binding RNA polymerase II's phosphoCTD. These proteins, involved in DNA and RNA processes, suggest the phosphoCTD organizes broader nuclear functions beyond transcription.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- The C-terminal repeat domain (CTD) of RNA polymerase II undergoes phosphorylation during transcription.
- The role of the phosphorylated CTD (phosphoCTD) is primarily associated with transcription and RNA processing.
Purpose of the Study:
- To identify novel proteins that interact with the hyperphosphorylated CTD (phosphoCTD) of RNA polymerase II.
- To explore the functional implications of these interactions beyond known roles in transcription.
Main Methods:
- Interaction blot approach was used to screen the human nuclear proteome.
- Identification and characterization of proteins binding to the phosphoCTD.
Main Results:
- Eight novel proteins associating with the phosphoCTD were identified.
- Five of these proteins are involved in DNA and chromatin transactions (e.g., topoisomerase I, DNA methyltransferase 1, PARP-1, hnRNP U/SAF-A, hnRNP D).
- Three proteins are involved in pre-mRNA metabolism (CA150, NSAP1/hnRNP Q, hnRNP R).
Conclusions:
- The phosphoCTD interacts with proteins involved in diverse DNA transactions, suggesting roles beyond transcription and RNA processing.
- The phosphoCTD may play critical roles in genome integrity, epigenetic regulation, and nuclear organization.
- A model is proposed where the phosphoCTD acts as a major organizer of nuclear functions by interacting with various protein complexes.