Publication highlights

Here we showed that Sld3, which we previously identified as being one of two essential cyclin dependent kinase (CDK) substrates in replication, is a phosphopeptide binding protein which binds specifically to Mcm4 and Mcm6 when they have been phosphorylated by Dbf4 dependent kinase (DDK). Sld3 then directly recruits Cdc45 to MCM and, via CDK phosphorylation, recruits the remaining firing factors. We had previously shown that Sld3 is also one of two targets of the DNA damage checkpoint kinase involved in inhibiting origin firing in response to DNA damage. Thus, Sld3 plays key roles with all three kinases that regulate replication (CDK, DDK, Rad53).

In this and the accompanying paper (Yeeles et al. 2017 Mol Cel 65, 105-116) we describe the reconstitution of full chromatin replication. We first identified all of the factors required for complete and rapid replication of naked DNA. Then we identified and characterised factors required to replicate chromatinised templates. We showed FACT is essential for chromatin replication, whilst nucleosome remodellers and histone acetylases help chromatin replication. In addition, chromatin enforces origin specificity and Okazaki fragment processing. Finally, we found that histones are efficiently transferred to nascent DNA.

This paper provided the first evidence that stem cells in the adult mouse hippocampus are heterogeneous in their behaviour, with most stem cells differentiating and leaving the niche after they have become active but a small fraction returning to a shallow state of quiescence. These “resting cells” have an essential role in the long-term maintenance of an active stem cell pool.

This paper established that intestinal epithelial cells use BTNL/Btnl molecules to select for and regulate tissue-specific gamma delta T cell compartments. It established a biological mechanism by which epithelial cells communicate with local T cells at steady-state (“normality sensing”). Following on from our prototypic discovery of such a mechanism in mouse skin, the work established conservation of the process across tissues as well as across species. The system is unperturbed by microbial colonisation.

This study showed that epigenetic mechanisms play an important role in generating functional heterogeneity within tumours, and can override genetic alterations that initiate the disease by inhibiting cell proliferative potential during tumour growth. The finding that heterogeneous patterns of H1.0 are broadly observed in cancer and that H1.0 is an independent predictor of patient survival in multiple types of solid tumours makes a strong case for a general role of epigenetic regulators in cancer. Mechanistic characterisation of how H1.0 controls malignant self-renewing states also provided insights into general mechanisms through which the linker histone regulates gene expression.

We investigated how intratumour heterogeneity affects response to checkpoint blockade and how cancers might be treated based on evolutionary principles. Durable clinical benefit to checkpoint blockade in lung cancer and melanoma was associated with a high burden of clonal neoantigens; in contrast, tumours that progressed early on therapy had a higher burden of heterogeneous neoantigens. We could predict clonal neoantigens present in every tumour cell and identify immune cells that recognise them, suggesting that development of adoptive T cell or vaccination strategies targeting such clonal neoantigens might limit therapeutic escape and resistance mechanisms.

Using new high-throughput imaging designed for rare cell subsets, we revealed that germinal centre B cells form uniquely patterned immune synapses to bind antigens. The separation of antigen into small clusters, along with specific cytoskeletal organisation results in enhanced mechanical forces transferred onto the B cell receptor-antigen bonds, increasing the mechanical affinity-discrimination power of germinal centre B cells compared to other B cell subsets. The work implicated germinal centre B cell mechanics in selection of high-affinity B cell clones in antibody responses and introduced novel DNA nanosensors for measuring cellular forces.

We demonstrated that mechanical forces and not enzymatic liberation are the physiological mechanism for acquisition of antigens by B cells from live presenting cells. Using DNA-based nanosensors we showed that B cell affinity discrimination is regulated by physical properties of the antigen-presenting cells and identified follicular dendritic cells as a stiff antigen presenting subset that promotes B cell affinity discrimination in germinal centres.

In this study we identified the WNK1 kinase as a negative regulator of CD4+ T cell adhesion and a positive regulator of T cell migration. Furthermore, we showed that WNK1 controls migration through the OXSR1 and STK39 kinases and the SLC12A2 ion co-transporter. This was an unexpected finding since WNK1 had been previously shown to regulate salt homeostasis in the kidney. Our study is the first to have implicated movement of Na+, K+ and Cl- ions in the regulation of T cell migration.

This work used high-resolution PET/CT imaging to establish for the first time in humans the existence of a high-risk asymptomatic transition state between latent infection and active disease. The technique is thus a phenotypic benchmark for further experimental medicine studies of interventions to prevent progression of asymptomatic subclinical tuberculosis.