Cyclin-Cyclin-dependent Kinase Regulatory Response Is Linked to Substrate Recognition

Abstract

Cyclin/cyclin-dependent kinase (CDK) complexes are critical regulators of cellular proliferation.A complex network of regulatory mechanisms has evolved to control their activity, including activating and inactivating phosphorylation of the catalytic CDK subunit and inhibition through specific regulatory proteins. Primate herpesviruses, including the oncogenic Kaposi sarcoma herpesvirus, encode cyclin D homologues. Viral cyclins have diverged from their cellular progenitor in that they elicit holoenzyme activity independent of activating phosphorylation by the CDK-activating kinase and resistant to inhibition by CDK inhibitors. Using sequence comparison and site-directed mutagenesis, we performed molecular analysis of the cellular cyclin D and the Kaposi sarcoma herpesvirus-cyclin to delineate the molecular mechanisms behind their different behavior. This provides evidence that a surface recognized for its involvement in the docking of CIP/KIP inhibitors is required and sufficient to modulate cyclin-CDK response to a range of regulatory cues, including INK4 sensitivity and CDK-activating kinase dependence. Importantly, amino acids in this region are critically linked to substrate selection, suggesting that a mutational drift in this surface simultaneously affects function and regulation. Together our work provides novel insight into the molecular mechanisms governing cyclin-CDK function and regulation and defines the biological forces that may have driven evolution of viral cyclins.Cyclins are regulatory subunits of the cyclin-dependent family of heterodimeric serine/threonine kinases (CDKs) 2 (1). Specific cyclin-CDK complexes drive progression through the cell division cycle, and their controlled activation is key for appropriate and ordered cell cycle transit (2). Deregulation of cyclin-CDKs is a recognized and probably causative event in cancer development and may be linked to uncontrolled and inappropriate engagement in cell cycle activities (3-5). In normal cells, a dense network of regulatory mechanisms controls duration and timing of these kinases (6, 7). Biochemical studies combined with exemplary crystal structures have provided insights into the mechanisms of cyclin-CDK regulation (8 -10).Cyclins selectively associate with specific CDKs. This association induces extensive conformational changes in the CDK subunit, leading to alignment of residues in the active site as well as rearrangement of the flexible T loop that blocks the entrance to the catalytic cleft in the monomeric CDKs. Phosphorylation of a residue within the T loop by the CDK-activating kinases (CAK) is then required to fully activate the kinase complex (11).A further level of regulation is provided by two classes of inhibitory proteins (CDKIs) (12). The INK4 family, exemplified by p16INK4a (CDKN2A), p15INK4b (CDKN2B), p18INK4c (CDKN2C), and p19INK4d (CDKN2D), selectively binds and affects the activity of CDK4 and CDK6. Cyclin D-CDK4 and cyclin D-CDK6 complexes initiate phosphorylation and inactivation of the retinoblastoma tumor suppresso...

Integration of Network Pharmacology and Experimental Validation to Explore Jixueteng - Yinyanghuo Herb Pair Alleviate Cisplatin-Induced Myelosuppression

“…Cyclin dependent protein kinase holoenzyme complex was enriched by GO-CC (pink histogram) which was critical regulators of cellular proliferation. 20 Membrane raft, membrane microdomain, and transcription regulator complex showed a large proportion in GO-BP (orange histogram). Meanwhile, KEGG enrichment analysis enriched 204 pathways, indicating the primary pathways included IL-17 signaling pathway (hsa04657), TNF signaling pathway (hsa04668), 21 PI3K-Akt signaling pathway (hsa04151), 22 mitogen-activated protein kinase (MAPK) signaling pathway 23 , 24 (hsa04010) ( Figure 5E ).…”

Study of cytostatic and cytotoxic characteristics of modified peptide CDK4/6 inhibitors – functional analogs of p16INK4a (90-97)

“…В настоящее время описано большое количество так называемых структурных CKIs. Наиболее изученными CKIs являются белки 2 семейств -INK4 и CIP / KIP, при взаимодействии CKIs с CDKs происходят конформационные трансформации последних, что препятствует образованию комплексов CDK-циклин [7]. Дисрегуляция циклиновых комплексов отмечается при многих типах онкологических заболеваний, что приводит к нарушению координации клеточного цикла и процессов пролиферации, способствует бесконтрольному клеточному росту [8].…”

Clonagem, expressão, purificação e caracterização da proteína ciclina D3 obtida pela expressão em sistema bacteriano (>i<Escherichia coli>/i<)

“…Transições críticas do ciclo celular eucariótico são reguladas por eventos padrões de fosforilação de proteínas governadas predominantemente pela atividade catalítica de CDKs (GALLORINI et al, 2012). A atividade das quinases é regulada entre si por reações de fosforilação-desfosforilação sítio-específico (KREK e NIGG, 1991;SOLOMON, 1994), e no caso das CDKs, a associação com subunidades regulatórias positivas (ciclinas) (HUNT, 1991) e negativas (inibidores de CDKs -CKIs) (ELLEDGE e HARPER, 1994;CUOMO et al, 2011).…”