Recent research has highlighted a growing focus on stimuli-responsive surfactant wormlike micelles (WLMs), particularly those with switchability. Here we report CO2-switchable WLMs based on the commercial anionic surfactant sodium dodecyl sulfate (SDS) and N,N,N',N'-tetramethyl-1,3-propanediamine (TMPDA) mixed in a mole ratio of 2:1. When CO2 is bubbled into an aqueous mixture of these reactants, the TMPDA molecules are protonated to form quaternary ammonium species, two of which in the same protonated TMPDA molecule "bridge" two SDS molecules by noncovalent electrostatic attraction, behaving like a pseudogemini surfactant and forming viscoelastic WLMs as verified by cryo-TEM. Upon removal of CO2, the quaternized spacers are deprotonated back to tertiary amines, dissociating the pseudogeminis back to conventional SDS molecules that form low-viscosity spherical micelles. Such a reversible sphere-to-worm transition could be repeated several cycles without a loss of response to CO2.

A CO 2 -switchable wormlike micellar system was fabricated using Nerucamidopropyl-N,N-dimethylamine without any hydrotropes. Its viscoelasticity varies by five orders of magnitude when cyclically bubbling CO 2 and air at ambient temperature and pressure without the need for heating, reflecting changes in aggregate morphology from entangled worms to spherical micelles.

Central to the recognition, signaling, and repair of DNA double-strand breaks (DSBs) are the MRE11-RAD50-NBS1 (MRN) complex and mediator of DNA damage checkpoint protein 1 (MDC1), the interplay of which is essential for initiation and amplification of the DNA damage response (DDR). The intrinsic rule governing the regulation of the function of this molecular machinery remains to be investigated. We report here that the ubiquitin-specific protease USP7 was physically associated with the MRN-MDC1 complex and that the MRN-MDC1 complex acted as a platform for USP7 to efficiently deubiquitinate and stabilize MDC1, thereby sustaining the DDR. Accordingly, depletion of USP7 impaired the engagement of the MRN-MDC1 complex and the consequent recruitment of the downstream factors p53-binding protein 1 (53BP1) and breast cancer protein 1 (BRCA1) at DNA lesions. Significantly, USP7 was overexpressed in cervical cancer, and the level of its expression positively correlated with that of MDC1 and worse survival rates for patients with cervical cancer. We demonstrate that USP7-mediated MDC1 stabilization promoted cervical cancer cell survival and conferred cellular resistance to genotoxic insults. Together, our study reveals a role for USP7 in regulating the function of the MRN-MDC1 complex and activity of the DDR, supporting the pursuit of USP7 as a potential therapeutic target for MDC1-proficient cancers.