Biology subjects

Kang, J. Y.

Publications and source records attributed to Kang, J. Y..

6 recordsLinked to original sources

bioRxiv2026

Maternal high-fat diet drives sex-specific microglia remodeling of serotonergic reward circuits

Maternal nutrition shapes offspring brain development and influences neurodevelopmental disorder risk, but the underlying mechanisms remain unclear. In mice, maternal high-fat diet exposure disrupted microglia-serotonin interactions during a critical postnatal period, producing persistent, sex-specific mesolimbic alterations. Male but not female offspring showed increased serotonergic fiber density in the nucleus accumbens (NAc), coincident with reduced microglial phagocytosis of serotonergic projections. Microglial 5-HT2C receptor signaling is a key regulator of this process. Viral over expression in microglia, mimicking diet-induced upregulation, was sufficient to cause serotonergic hyperinnervation. By adulthood, male offspring displayed increased NAc serotonin release and projection-specific changes in dorsal raphe physiology. These circuit alterations accelerated reward-motivated learning, a phenotype reproduced by chemogenetic activation of NAc-projecting serotonergic neurons. Together, these findings reveal a novel mechanism by which maternal diet programs serotonergic circuit assembly and behavior in a sex-specific manner, providing a potential link between early-life metabolic inflammation and lifelong serotonergic dysfunction.

neuroscience↗

bioRxiv2022

Leadership in PhD (LeaP): a longitudinal leadership skill building program for underrepresented biomedical research trainees

AO_SCPLOWBSTRACTC_SCPLOWIncreasing diversity in the biomedical research workforce is a critical national issue. Particularly concerning is the lack of representation at more advanced career stages/in leadership positions. While there are numerous institutional initiatives promoting professional research skills (i.e. grant writing, presenting, networking) for underrepresented (UR) PhD trainees, there are comparatively fewer opportunities for leadership development. We present a blueprint for Leadership in PhD (LeaP), a cohort-based program aiming to equip UR biomedical research trainees with skills to succeed as academic, industry, and community leaders. In contrast to intensive short-term programs or workshops, LeaP is a longitudinal 4-year experience with an emphasis on self-directed and experiential learning. First year trainees receive foundational didactic instruction on core leadership concepts coupled with facilitated peer discussions and one-on-one coaching support. We outline a program evaluation framework that assesses student learning, satisfaction, and program efficacy. Evaluation data from the inaugural year is presented and discussed.

scientific communication and education↗

bioRxiv2022

An ensemble of interconverting conformations of the elemental paused transcription complex creates regulatory options

Transcriptional pausing underpins regulation of cellular RNA synthesis but its mechanism remains incompletely understood. Sequence-specific interactions of DNA and RNA with the dynamic, multidomain RNA polymerase (RNAP) trigger reversible conformational changes at pause sites that temporarily interrupt the nucleotide addition cycle. These interactions initially rearrange the elongation complex (EC) into an elemental paused EC (ePEC). ePECs can form longer-lived PECs by further rearrangements or interactions of diffusible regulators. For both bacterial and mammalian RNAPs, a half-translocated state in which the next DNA template base fails to load into the active site appears central to the ePEC. Some RNAPs also swivel interconnected modules that may stabilize the ePEC. However, it is unclear if swiveling and half-translocation are requisite features of a single ePEC state or if multiple ePEC states exist. Here we use cryo-EM analysis of ePECs with different RNA-DNA sequences combined with biochemical probes of ePEC structure to define an interconverting ensemble of ePEC states. ePECs occupy either pre- or half-translocated states but do not always swivel, indicating that difficulty in forming the post-translocated state at certain RNA-DNA sequences may be the essence of the ePEC. The existence of multiple ePEC conformations has broad implications for transcriptional regulation. SIGNIFICANCETranscriptional pausing provides a hub for gene regulation. Pausing provides a timing mechanism to coordinate regulatory interactions, co-transcriptional RNA folding and protein synthesis, and stop signals for transcriptional termination. Cellular RNA polymerases (RNAPs) are complex, with multiple mobile modules shifting positions to control its catalytic activity and pause RNAP in response to DNA-encoded pause signals. Understanding how these modules move to enable pausing is crucial for a mechanistic understanding of gene regulation. Our results clarify the picture significantly by defining multiple states among which paused RNAP partitions in response to different pause signals. This work contributes to an emerging theme wherein multiple interconverting states of the RNAP proceed through a pathway (e.g., initiation or pausing), providing multiple opportunities for regulation.

biochemistry↗

bioRxiv2020

Structural basis for transcription complex disruption by the Mfd translocase

Transcription-coupled repair (TCR) is a sub-pathway of nucleotide excision repair (NER) that preferentially removes lesions from the template-strand (t-strand) that stall RNA polymerase (RNAP) elongation complexes (EC). Mfd mediates TCR in bacteria by removing the stalled RNAP concealing the lesion and recruiting Uvr(A)BC. We used cryo-electron microscopy to visualize Mfd engaging with a stalled EC and attempting to dislodge the RNAP. We visualized seven distinct Mfd-EC complexes in both ATP and ADP-bound states. The structures explain how Mfd is remodeled from its repressed conformation, how the UvrA-interacting surface of Mfd is hidden during most of the remodeling process to prevent premature engagement with the NER pathway, how Mfd alters the RNAP conformation to facilitate disassembly, and how Mfd forms a processive translocation complex after dislodging the RNAP. Our results reveal an elaborate mechanism for how Mfd kinetically discriminates paused from stalled ECs and disassembles stalled ECs to initiate TCR.

biophysics↗

bioRxiv2018

Eliminating effects of particle adsorption to the air/water interface in single-particle cryo-electron microscopy: Bacterial RNA polymerase and CHAPSO

Preferred particle orientation presents a major challenge for many single particle cryoelectron microscopy (cryo-EM) samples. Orientation bias limits the angular information used to generate three-dimensional maps and thus affects the reliability and interpretability of the structural models. The primary cause of preferred orientation is presumed to be due to adsorption of the particles at the air/water interface during cryo-EM grid preparation. To ameliorate this problem, detergents are often added to cryo-EM samples to alter the properties of the air/water interface. We have found that many bacterial transcription complexes suffer severe orientation bias when examined by cryo-EM. The addition of non-ionic detergents, such as NP-40, does not remove the orientation bias but the Zwitter-ionic detergent CHAPSO significantly broadens the particle orientation distributions, yielding isotropically uniform maps. We used cryoelectron tomography to examine the particle distribution within the ice layer of cryo-EM grid preparations of Escherichia coli 6S RNA/RNA polymerase holoenzyme particles. In the absence of CHAPSO, essentially all of the particles are located at the ice surfaces. CHAPSO at the critical micelle concentration eliminates particle absorption at the air/water interface and allows particles to randomly orient in the vitreous ice layer. We find that CHAPSO eliminates orientation bias for a wide range of bacterial transcription complexes containing E. coli or Mycobacterium tuberculosis RNA polymerases. Findings of this study confirm the presumed basis for how detergents can help remove orientation bias in cryo-EM samples and establishes CHAPSO as a useful tool to facilitate cryo-EM studies of baterial transcription complexes.

biophysics↗

bioRxiv2018

Structural basis for transcript elongation control by NusG/RfaH universal regulators

NusG/RfaH/Spt5 transcription elongation factors are the only transcription regulators conserved across all life. In bacteria, NusG regulates RNA polymerase (RNAP) elongation complexes (ECs) across most genes, enhancing elongation by suppressing RNAP backtracking and also coordinating {rho}-dependent termination and translation. RfaH is a specialized NusG paralog that engages the EC at ops sites and subsequently excludes NusG and suppresses both backtrack and hairpin-stabilized pausing. We used single-particle cryo-EM to determine structures of ECs at ops with NusG or RfaH. Both factors chaperone base pairing of the EC upstream duplex DNA to suppress backtracking. RfaH loads onto the EC by specific recognition of an ops hairpin in the single-stranded nontemplate DNA. Binding of both NusG and RfaH is incompatible with the swiveled RNAP conformation necessary for hairpin-stabilized pausing, but only RfaH fully counteracts swiveling to suppress pausing. The universal conservation of NusG/RfaH/Spt5 suggests that the molecular mechanisms uncovered here are widespread.

biophysics↗