PXD053627-1

PXD053627 is an original dataset announced via ProteomeXchange.

Title	Integrative Proteomics Identifies MePCE as a Substrate of CDK9 for Releasing P-TEFb from 7SK snRNP Under Genotoxic Stress
Description	The dynamic phosphorylation process regulated by the positive transcription elongation factor b (P-TEFb), a CDK9-cyclin T heterodimer, is critical for transcription elongation of numerous mammalian genes. Most P-TEFb in cells are normally sequestered in the 7SK snRNP, and their release from this complex is well-controlled to maintain proper cell homeostasis and growth. The comprehensive profiling of CDK9 substrates is essential for understanding diverse functions of P-TEFb in controlling gene expression. Here, integrative proteomics methodologies are developed to globally identify the potential substrates of CDK9 in vivo. Our results show that the 7SK methylphosphate capping enzyme MePCE is directly phosphorylated by CDK9 within the 7SK snRNP, which is known to exhibit little kinase activity toward other known CDK9 substrates. Upon ultraviolet radiation, MePCE becomes phosphorylated, leading to the dissociation of 7SK snRNP and release of P-TEFb to activate transcription. Meanwhile, the phosphorylation of MePCE does not affect its methyltransferase activity toward 7SK RNA. Our data suggest that even though CDK9 in 7SK snRNP has little kinase activity toward external substrates, it can phosphorylate the snRNP integral component MePCE, which is required to release P-TEFb. This novel inside-to-outside mode of P-TEFb activation may serve as a critical checkpoint in regulating gene transcription under stressful conditions.
HostingRepository	iProX
AnnounceDate	2024-07-03
AnnouncementXML	Submission_2024-09-29_19:52:33.139.xml
DigitalObjectIdentifier
ReviewLevel	Peer-reviewed dataset
DatasetOrigin	Original dataset
RepositorySupport	Unsupported dataset by repository
PrimarySubmitter	Chunjing Chen
SpeciesList	scientific name: Homo sapiens; NCBI TaxID: 9606;
ModificationList	phosphorylated residue; (13)C labeled residue
Instrument	Orbitrap Fusion; Q Exactive

Revision	Datetime	Status	ChangeLog Entry
0	2024-07-03 20:43:55	ID requested
⏵ 1	2024-09-29 19:52:33	announced

Dataset with its publication pending

submitter keyword: Phosphorylation

Phosphoproteomics

MePCE

CDK9 substrates

P-TEFb

Xiang Gao
contact affiliation	Xiamen University
contact email	xgao@xmu.edu.cn
lab head
Chunjing Chen
contact affiliation	Xiamen University
contact email	chencj_1106@163.com
dataset submitter

iProX dataset URI