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Alterations in gamma-band auditory steady-state response (ASSR) are the most robust finding of abnormal neural oscillations in patients with first-episode (FES) and chronic schizophrenia. Gamma-band ASSRs may indicate GABAergic interneuron dysfunction. Nevertheless, it is unknown whether abnormal gamma-band ASSRs are present before the onset of psychosis. Subjects were 15 ultra-high-risk (UHR) individuals, 13 FES patients, and 21 healthy control (HC) subjects. We performed electroencephalogram recordings and measured ASSRs in each group as they were presented with click trains at 20, 30, and 40 Hz. We then conducted time-frequency analyses and calculated intertrial phase coherence and event-related spectral perturbation. The time course of gamma-band ASSRs showed significantly different features among groups. Compared with the HC group, the UHR group was characterized by intact early-latency (0-100 ms) and reduced late-latency (300-500 ms) ASSRs. In contrast, both early- and late-latency ASSRs were significantly reduced in the FES group. Gamma-band ASSRs were correlated with clinical symptoms and attentional functioning in FES (|rs| > 0.70). These results suggest differential alterations of gamma-band ASSRs between UHR and FES groups. The late-latency ASSR alteration may represent a biomarker for early detection of psychosis, while the early-latency ASSR abnormality may develop through the onset of psychosis.

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XPA is a zinc finger DNA-binding protein, which is missing or altered in group A xeroderma pigmentosum cells and known to be involved in the damage-recognition step of the nucleotide excision repair (NER) processes. Using the yeast two-hybrid system to search for proteins that interact with XPA, we obtained the 34-kDa subunit of replication protein A (RPA, also known as HSSB and RFA). RPA is a stable complex of three polypeptides of 70, 34, 11 kDa and has been shown to be essential in the early steps of NER as well as in replication and recombination. We also demonstrate here that the RPA complex associates with XPA. These results suggest that RPA may cooperate with XPA in the early steps of the NER processes.

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