Increased HEXIM1 expression during erythroleukemia and neuroblastoma cell differentiation.

The HEXIM1 protein, in association with 7SK snRNA, binds and inhibits the kinase activity of P-TEFb (CDK9/cyclin T). P-TEFb activity is crucial for efficient transcription elongation of viral and cellular genes. HEXIM1 was originally isolated as a protein up-regulated by hexamethylene bisacetamide (HMBA), a prototypical inducer of differentiation.

Transcription-dependent association of multiple positive transcription elongation factor units to a HEXIM multimer.

The positive transcription elongation factor (P-TEFb) comprises a kinase, CDK9, and a Cyclin T1 or T2. Its activity is inhibited by association with the HEXIM1 or HEXIM2 protein bound to 7SK small nuclear RNA. HEXIM1 and HEXIM2 were found to form stable homo- and hetero-oligomers.

Coding polymorphisms in the parkin gene and susceptibility to Parkinson disease.

Background: Mutations in the parkin gene, an E3 protein-ubiquitin ligase, cause autosomal recessive early-onset Parkinson disease (PD). The role of polymorphisms in the parkin gene as risk factors for PD is still unclear, as the results in the literature are contradictory.

Patients: We compared the allele and genotype frequencies of the Ser167Asn, Arg366Trp, Val380Leu, and Asp394Asn polymorphisms in 194 patients with PD (92 familial and 102 sporadic) and 125 control subjects.