Biology subjects

Khandagale, P.

Publications and source records attributed to Khandagale, P..

3 recordsLinked to original sources

bioRxiv2025

SLFN11 puts the brakes on Alternative lengthening of telomeres

Alternative lengthening of telomeres (ALT) is a homologous recombination-dependent mechanism maintaining telomere length in approximately 10-15% of all cancers that are telomerase (TERT) negative. ALT is most prominent in osteosarcoma. Although many ALT cells feature loss of the ATRX/DAXX chromatin remodeling complex, ATRX/DAXX deficiency alone is insufficient to trigger ALT. Here, we provide evidence that Schlafen 11 (SLFN11) acts as a suppressor of the telomeric ALT pathway. TERT-negative osteosarcoma U2-OS (ALT) cells, that normally lack SLFN11 expression, show SLFN11 localization to telomeres upon doxycycline-induced SLFN11 expression. This re-expression markedly suppresses ALT activity, as evidenced by reduced ALT-associated PML bodies (APBs) and decreased levels of Telomeric Repeat-containing RNA (TERRA). SLFN11 re-expression also attenuates the telomeric DNA damage response (DDR) and induces telomere destabilization in ALT cells. Furthermore, SLFN11 suppresses ALT induction in ATRX-depleted prostate carcinoma DU145 cells. Collectively, our findings identify SLFN11 as a negative telomeric regulator of the ALT pathway, indicating that its loss, together with ATRX/DAXX inactivation, contributes to ALT activation.

cell biology↗

bioRxiv2020

Identification of PCNA interacting protein motifs in human DNA polymerase delta

DNA polymerase delta (Pol{delta}) is a highly processive essential replicative DNA polymerase. In humans, Pol{delta} holoenzyme consists of p125, p50, p68, and p12 subunits and recently, we have shown that p12 exists as a dimer. Extensive biochemical studies suggest that all the subunits of Pol{delta} interact with the processivity factor proliferating cell nuclear antigen (PCNA) to carry out a pivotal role in genomic DNA replication. While PCNA interaction protein (PIP) motifs in p68, p50 and p12 have been mapped, the PIP in p125, the catalytic subunit of the holoenzyme, remains elusive. Therefore, in this study by using multiple approaches we have conclusively mapped a non-canonical PIP box from residues 999VGGLLAFA1008 in p125, which binds to inter domain-connecting loop of PCNA with high affinity. Collectively, including previous studies, we conclude that similar to S. cerevisiae Pol{delta}, each of the human Pol{delta} subunits possess motif to interact with PCNA and significantly contribute towards the processive nature of this replicative DNA polymerase.

biochemistry↗

bioRxiv2019

Human DNA polymerase delta is a pentameric complex with dimeric p12 subunit: Implications in enzyme architecture and PCNA interaction

Human DNA polymerase delta (Pol{delta}), a holoenzyme consisting of p125, p50, p68 and p12 subunits, plays an essential role in all the three DNA transaction processes. Herein, using multiple physicochemical and cellular approaches we found that the p12 protein forms a dimer in solution. In vitro reconstitution and pull-down of cellular Pol{delta} by tagged p12 authenticates pentameric nature of this critical holoenzyme. Further, a consensus PIP motif at the extreme carboxyl terminal tail and a homodimerization domain at the amino-terminus of the p12 subunit were identified. Our mutational analyses of p12 subunit suggest that 3RKR5 motif is critical for dimerization that facilitates p12 binding to IDCL of PCNA via its PIP motif 98QCSLWHLY105. Additionally, we observed that oligomerization of the smallest subunit of Pol{delta}s is evolutionarily conserved as Cdm1 of S. pombe also dimerzes. Thus, we suggest that human Pol{delta} is a pentameric complex with a dimeric p12 subunit; and discuss implications of p12 dimerization in regulating enzyme architecture and PCNA interaction during DNA replication.

molecular biology↗