Biology subjects

Roninson, I. B.

Publications and source records attributed to Roninson, I. B..

3 recordsLinked to original sources

bioRxiv2023

Knockout of cyclin dependent kinases 8 and 19 leads to depletion of cyclin C and suppresses spermatogenesis and male fertility in mice

Paralogs CDK8 and CDK19 are regulatory kinases associated with the transcriptional Mediator complex. We have e generated mice with the systemic inducible Cdk8 knockout on the background of Cdk19 constitutive knockout. Cdk8/19 double knockout (iDKO) males, but not single Cdk8 and Cdk19 KO, had an atrophic reproductive system and were infertile. The iDKO males lacked postmeiotic spermatids and spermatocytes after meiosis I pachytene. Testosterone levels were decreased whereas the amounts of the luteinizing hormone were unchanged. Single cell RNA sequencing showed marked differences in the expression of steroidogenic genes (such as Cyp17a1, Star and Fads) in Leydig cells concomitant with alterations in Sertoli cells and spermatocytes likely associated with impaired synthesis of steroids. Star and Fads were also downregulated in cultivated Leydig cells after iDKO. The treatment of primary Leydig cells culture with a CDK8/19 inhibitor did not induce the same changes in gene expression as iDKO, and prolonged treatment of mice with a CDK8/19 inhibitor did not affect the size of testes. iDKO, in contrast to single knockouts or treatment with a CDK8/19 kinase inhibitor, led to depletion of cyclin C (CcnC), the binding partner of CDK8/19 that has been implicated in CDK8/19-independent functions. This suggests that the observed phenotype was likely mediated through kinase-independent activities of CDK8/19, such as CcnC stabilization.

developmental biology↗

bioRxiv2023

CDK8/19 Inhibition Attenuates G1 Arrest Induced by BCR-ABL Antagonists and Accelerates Death of Chronic Myelogenous Leukemia Cells

Imatinib mesylate (IM) and other BCR-ABL tyrosine kinase inhibitors (BCR-ABLi) are the mainstay of chronic myelogenous leukemia (CML) treatment. However, activation of circumventing signaling pathways and quiescence may limit BCR-ABLi efficacy. CDK8/19 Mediator kinases have been implicated in the emergence of non-genetic drug resistance. Dissecting the effects of pharmacological CDK8/19 inhibition on CML survival in response to BCR-ABLi, we found that a selective, non-toxic CDK8/19 inhibitor (CDK8/19i) Senexin B (SenB) and other CDK8/19i sensitized K562 cells to different BCR-ABLi via attenuation of cell cycle arrest. In particular, SenB prevented IM-induced upregulation of genes that negatively regulate cell cycle progression. SenB also antagonized IM-activated p27Kip1 elevation thereby diminishing the population of G1-arrested cells. After transient G1 arrest, cells treated with IM+SenB re-entered the S phase, where they were halted and underwent replicative stress. Consequently, the combination of IM and SenB intensified apoptotic cell death, measured by activation of caspase 9 and 3, subsequent cleavage of poly(ADPriboso)polymerase 1, positive Annexin V staining and increase of subG1 fraction. In contrast, IM-treated BCR-ABL-positive KU812 CML cells, which did not induce p27Kip1, readily died regardless of SenB treatment. Thus, CDK8/19i prevent the quiescence-mediated escape from BCR-ABLi-induced apoptosis, suggesting a strategy for avoiding the CML relapse.

cancer biology↗

bioRxiv2023

CDK19 and CDK8 Mediator kinases drive androgen-independent in vivo growth of castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) remains incurable due to its high plasticity. We found that Mediator kinases CDK8 and CDK19, pleiotropic regulators of transcriptional reprogramming, are differentially affected by androgen, which downregulates CDK8 and upregulates CDK19. Accordingly, expression of CDK8 decreases while CDK19 increases during prostate carcinogenesis, but both CDK19 and CDK8 are upregulated in metastatic CRPC. Genetic inactivation of CDK8 and CDK19 suppresses CRPC tumor growth in castrated male mice and renders CRPC responsive to androgen deprivation. Restoration of active CDK19 or CDK8 kinases reverses this phenotype, indicating that CRPC becomes dependent on Mediator kinase activity for in vivo growth under the conditions of androgen deprivation. Selective CDK8/19 inhibitors suppress androgen-independent growth of cell line-based and patient-derived CRPC xenografts, whereas prolonged inhibitor treatment induces tumor regression and even leads to cures. Mediator kinase activity was found to affect tumor and stromal gene expression preferentially in castrated mice, orchestrating castration-induced transcriptional reprogramming. These results warrant the exploration of Mediator kinase inhibitors for CRPC therapy.

cancer biology↗