Zhou, Q.-X. | bioRxiv Science

bioRxiv2024

Stabilization of Integrator/INTAC by the small but versatile DSS1 protein

Integrator-PP2A (INTAC) is a highly modular complex orchestrating the transition of paused RNA polymerase II into productive elongation or promoter-proximal premature termination, with its loss resulting in transcription dysregulation and genome instability. Here, we identify human DSS1--a flexible 70-residue protein found in multiple functionally diverse complexes including the 26S proteasome--as an integral subunit of the INTAC backbone. Structural analysis of DSS1-INTAC, both alone and in association with paused polymerase, demonstrates intimate interactions between DSS1 and the INTAC backbone subunit INTS7. We identify tryptophan 39 of DSS1 as being critical for interacting with INTAC and find that mutating this residue disrupts DSS1s interaction with INTAC, while maintaining DSS1s interaction with the proteasome. This substitution not only destabilizes INTAC and therefore INTAC-dependent transcriptional regulation, but also reveals that INTAC is DSS1s major chromatin-bound form. Together, our findings reveal the essential role of the versatile DSS1 protein in the structure and regulatory functions of INTAC.

molecular biology↗

bioRxiv2023

Hippocampal Dipeptidyl Peptidase 9 Bilaterally Modulates Memory via its Enzymatic Activity

It has been reported that peripherally expressed subtypes of the dipeptidyl peptidase (DPP) family, such as DPP4, modulate memory. However, interestingly whether DPP9 which one of the central nervous systems (CNS) enriched isoforms, regulates memory has not been elucidated yet. Here, we report that DPP9, which is found almost exclusively in neurons, is highly expressed and has high enzyme activity in many brain regions, especially in the hippocampus. Hippocampal DPP9 expression increases after fear memory formation. Fear memory was weakened by DPP9 knockdown and enhanced by DPP9 protein overexpression in the hippocampus. According to subsequent hippocampal proteomics, multiple pathways were enriched by DPP9 expression changes, including the peptidase pathway, which can be bidirectionally regulated by DPP9, and pathways involved in the regulation of synaptic plasticity. DPP9 interacts with its enzymatic substrate neuropeptide Y (NPY) in neurons directly. Hippocampal long-term potentiation (LTP), a form of synaptic plasticity, further confirmed the key role of DPP9 in decreasing LTP through DPP9 knockdown and enhancing LTP through its overexpression. Moreover, inhibiting DPP9 enzyme activity impairs both plasticity and memory. Besides, Affinity purification mass spectrometry (AP-MS) revealed that DPP9-interacting proteins are involved in the functions of dendritic spines and axons. By combining AP-MS and proteomics, DPP9 was shown to play a role in regulating actin functions. Taken together, our findings reveal that DPP9 affects the CNS not only through enzymatic activity but also through protein-protein interactions. This study provides new insights into the molecular mechanisms of memory and DPP family functions.

neuroscience↗