The middle and the end

Abstract

Welcome to ‘The Middle & The End’, an EMBO Journal focus review series on centromere and telomere biology. The molecular biology of DNA and chromosomes has always been a centre of attention for readers and contributors of The EMBO Journal alike since its inception 27 years ago. Those years have seen amazing progress in our understanding of these notable chromosomal regions, yet even in the light of most recent advances it is clear that a lot more is yet to be deciphered—figuratively speaking, we are still far from the ‘end’ in terms of learning and understanding them, but we may well be in the very ‘middle’ of things by now. Having a middle and an end is a privilege of eukaryotic chromosomes, which—in contrast to the circular DNA of typical prokaryotes—are usually linear, a feature that endows them with characteristic properties as well as problems. For one, ends need to be protected and maintained, despite the intricacies of semi‐conservative replication and in the face of DNA break surveillance mechanisms liable to attempt their repair. The middle, on the other hand, is commonly the place for spindle microtubule attachment and thus important for chromosome segregation. In light of these peculiarities, centromeres and telomeres have become highly specialized compared with the bulk of eukaryotic chromosomes, which fulfills the more intuitive (and most fundamental) role of DNA, to encode genes for proteins or RNAs and to regulate their expression. This specialization of centromeres and telomeres is reflected at numerous levels, starting with DNA sequence through chromatin structure to the recruitment and function of specialized structural and signalling …