Di Stefano, G. | bioRxiv Science

bioRxiv2021

RAD51 nuclear recruitment and inhibition towards innovative strategies against pancreatic cancer

RAD51, a key player in the homologous recombination (HR) mechanism, is a critical protein to preserve genomic stability. BRCA2, upon DNA damage, promotes RAD51 fibrils disassembly and its nuclear recruitment. Here, we use BRC4, a peptide derived from the fourth BRC repeat of BRCA2; BRC4 induces RAD51 defibrillation through a domino effect, eroding fibrils from their termini, and yielding monomeric RAD51. The congruence among several techniques (static and dynamic light scattering, negative staining transmission electron microscopy (TEM), and microscale thermophoresis) allows an accurate estimation of the kinetic and thermodynamic parameters of this process. BRC4 lacks, however, a nuclear localization sequence; therefore, it cannot transport RAD51 into the nucleus, thus behaving as a RAD51 inhibitor. Cellular assays (BxPC-3, pancreatic cancer cells) indeed show that BRC4 efficiently inhibits HR and enhances the cytotoxic effect of cisplatin, a DNA-damaging drug. The present study sheds further light on the complexity of the HR pathway, paving the way for designing peptide and small organic molecule inhibitors of RAD51 as innovative anticancer and chemo/radiosensitizer compounds.

biophysics↗

bioRxiv2017

Characterising the short-term habituation of event-related evoked potentials

Fast-rising sensory events evoke a series of functionally heterogeneous event-related potentials (ERPs). Stimulus repetition at 1 Hz is known to induce a strong habituation of the largest ERP responses, the vertex waves, which are elicited by stimuli regardless of their modality7, provided that they are salient and behaviourally-relevant. In contrast, the effect of stimulus repetition on the earlier sensor)7 components of ERls has been less explored, and the few existing results are inconsistent. To characterize how the different ERP waves habituate over time, we recorded the responses elicited by 60 identical somatosensory stimuli (activating either non-nociceptive A {beta} or nociceptive A5 afferents), delivered at 1 Hz to healthy human participants. We show that the well-described spatiotemporal sequence of lateralised and vertex ERP components elicited by the first stimulus of the series is largely preserved in the smaller-amplitude, habituated response elicited by the last stimuli of the series. We also found that the earlier lateralised sensory waves habituate across the 60 trials following the same decay function of the vertex waves: this decay function is characterised by a large drop at the first stimulus repetition followed by smaller decreases at subsequent repetitions. Interestingly, the same decay functions described the habituation of ERPs elicited by repeated non-nociceptive and nociceptive stimuli. This study provides a neurophysiological characterization of the effect of prolonged and repeated stimulation on the main components of somatosensory ERPs. It also demonstrates that both lateralised waves and vertex waves are obligator}7 components of ERPs elicited by non-nociceptive and nociceptive stimuli.\n\nSignificance statementOur results provide a functional characterization of the decay of the different ERP components when identical somatosensory (nociceptive and non-nociceptive) stimuli are repeated at 1Hz. East-rising stimuli elicit ERPs obligator)7 contributed by both early lateralised components and late vertex components, even when stimulus repetition minimizes stimulus relevance. This challenges the view that lateralised waves are not obligatorily elicited by nociceptive stimuli. Furthermore, the lateralised and vertex waves habituate to stimulus repetition following similar decay functions, which are unlikely explained in terms of fatigue or adaptation of skin receptors.

neuroscience↗