Properties and mechanisms of PCNA (proliferating cell nuclear antigen) functions have been investigated for a long time and are studied in great detail. As follows from its name, most known PCNA functions (DNA replication, DNA repair, DNA recombination and others) are connected with cell proliferation and localization of this protein in nuclei. In addition, there is good reason to believe that PCNA also performs some functions in the cytoplasm. However, the possible role and mechanisms of PCNA action in the cytoplasm require careful study and clarification. Interestingly, such cells as neutrophils differ in that they are non-dividing on one hand and on the other hand contain a rather large amount of PCNA, which is localized only in the cytoplasm, that is, they are an ideal model for the study of cytoplasmic PCNA. Using cross-linkages with formaldehyde, we showed that this cytoplasmic PCNA is cross-linked in a similar way, that is, organized in the same way as the nuclear PCNA that is present in the proliferating cells. Previously, we showed that PCNA in such cells is organized into a dynamic complex of double trimer on the basis of the back-to-back principle (Naryzhny S.N. et al. (2005) J. Biol. Chem., 280, 13888). Apparently, such organization of this hub-protein allows it to better coordinate the processes taking place in the cytoplasm as well.
Svoĭstva i mekhanizmy funktsionirovaniia iadernogo antigena deliashchikhsia kletok (proliferating cell nuclear antigen, PCNA) issleduiutsia dovol'no davno i izucheny ves'ma detal'no. Naibolee izvestnye funktsii PCNA (replikatsiia DNK, reparatsiia DNK, rekombinatsiia DNK i dr.) sviazany s kletochnoĭ proliferatsieĭ i lokalizatsieĭ dannogo belka v iadre. Tem ne menee, est' veskie osnovaniia schitat', chto PCNA svoĭstvenny takzhe nekotorye funktsii i v tsitoplazme. Odnako vozmozhnaia rol' i mekhanizmy deĭstviia PCNA v tsitoplazme trebuiut tshchatel'nogo izucheniia i proiasneniia. V kontekste izucheniia tsitoplazmaticheskikh funktsiĭ PCNA neĭtrofily iavliaiutsia ideal'noĭ model'iu. S odnoĭ storony, oni iavliaiutsia nedeliashchimisia kletkami, a s drugoĭ storony – soderzhat dostatochno bol'shoe kolichestvo PCNA, kotoryĭ lokalizovan prakticheski tol'ko v tsitoplazme. Ispol'zuia sshivki formal'degidom, my pokazali, chto étot PCNA sshivaetsia odinakovym obrazom, to est', organizovan tak zhe, kak i iadernyĭ PCNA, kotoryĭ prisutstvuet v proliferiruiushchikh kletkakh. Ranee nami bylo pokazano (Naryzhny et al. (2005) J. Biol. Chem., 280, 13888), chto PCNA v takikh kletkakh mozhet nakhodit'sia v vide dinamicheskogo kompleksa iz dvoĭnykh trimerov. Po-vidimomu, takaia organizatsiia dannogo khab-belka pozvoliaiut emu luchshe koordinirovat' protsessy, proiskhodiashchie ne tol'ko v iadre, no i v tsitoplazme.
Keywords: PCNA; cytoplasm; double trimer; monomer; neutrophil; structure.