TopBP1 utilises a bipartite GINS binding mode to support genome replication

Activation of the replicative Mcm2-7 helicase by loading GINS and Cdc45 is crucial for replication origin firing, and as such for faithful genetic inheritance. Our biochemical and structural studies demonstrate that the helicase activator GINS interacts with TopBP1 through two separate binding surfaces, the first involving a stretch of highly conserved amino acids in the TopBP1-GINI region, the second a surface on TopBP1-BRCT4. The two surfaces bind to opposite ends of the A domain of the GINS subunit Psf1. Mutation analysis reveals that either surface is individually able to support TopBP1-GINS interaction, albeit with reduced affinity. Consistently, either surface is sufficient for replication origin firing in Xenopus egg extracts and becomes essential in the absence of the other. The TopBP1-GINS interaction appears sterically incompatible with simultaneous binding of DNA polymerase epsilon (Polε) to GINS when bound to Mcm2-7-Cdc45, although TopBP1-BRCT4 and the Polε subunit PolE2 show only partial competitivity in binding to Psf1. Our TopBP1-GINS model improves the understanding of the recently characterised metazoan pre-loading complex. It further predicts the coordination of three molecular origin firing processes, DNA polymerase epsilon arrival, TopBP1 ejection and GINS integration into Mcm2-7-Cdc45.

A comparison of computerized tomography and flair-SWI MRI results of patients with head injury attending the emergency department

OBJECTIVE

Detection of traumatic brain injury (TBI) is of vital importance in patients who apply to the emergency department with a history of trauma. The aim of initial imaging in patients with suspected TBI is to detect trauma-related injury quickly and accurately. In this study, the effectiveness of prospectively cranial computed tomography (CT) and fluid attenuation inversion recovery (FLAIR) and susceptibility weighted imaging (SWI) sequence magnetic resonance imaging (MRI) examination results of patients diagnosed with TBI in the emergency department in terms of bleeding detection was investigated in the light of the literature.

PATIENTS AND METHODS

Patients with traumatic brain injury who applied to the emergency department between 2016 and 2020 were included in this prospective study. Cranial CT and MRI images containing SWI-FLAIR sequence were taken on the same day, immediately after cranial CT, for a total of 500 patients.

RESULTS

In our study, TBI was detected in 242 males (70.8%) and 100 females (29.2%), for a total of 342 patients. The mean age was 41.45, the mean GCS was 13.35. There was a history of trauma such as falling in 155 patients (45.3%), traffic accidents in 171 patients (50%), and trauma in 16 patients (4.7%). In the comparative evaluation of CT and FLAIR-SWI MRI examinations no bleeding was detected in the FLAIR-SWI sections of 239 patients who did not have bleeding on CT; however, bleeding was detected in FLAIR-SWI sections in 14 patients who did not have bleeding on CT.

CONCLUSIONS

FLAIR-SWI MR, which is a more reliable examination method, should be performed before control CT, especially in patients with incompatible clinical and admission CT.