The sea urchin's siren

AbstractThis issue of Developmental Biology features articles that constitute a new wave of insights into how a genome interacts with itself (as DNA) and with effectors—proteins and probably RNAs, collectively operating as a kind of “cis-trans” dualism. We learned a test for allelism in genetics class that bore that Latin name but now it comes as a new day for biological science—a welcome era in which a phenomenon as complex as development can be envisioned from principles of chemical binding energy and specificity. The buzzword (the term is just—as there is deserved buzz) is that the genome is hard-wired, in the sense that it has been shaped to both encode and react to a regulatory network, of which it is itself a part. I here review some of the milestones of embryology in which the sea urchin was the key player, segueing into the modern era in which this organism launched an entirely new intellectual construct of genome organization and gene expression during development. This essay also contains a number of personal perspectives as well as some views on the overall epistemological fabric of developmental biology. Like all of us, I am excited to see the S. purpuratus genome appear and heartily congratulate, by writing this essay, the trailblazers whose intellectual courage and persistence has brought us to this happy position

Can telomerase be put in its place?

The Cajal body is an intriguing nuclear structure present in a great variety of plant, animal, and some fungal cells. Recent work on the ribonucleoprotein enzyme telomerase has indicated an unanticipated degree of intranuclear dynamics of both its RNA and protein subunits. In this issue, Jady et al. place the Cajal body on the intranuclear traffic route of telomerase RNA (Jady et al., 2004)

As functional nuclear actin comes into view, is it globular, filamentous, or both?

The idea that actin may have an important function in the nucleus has undergone a rapid transition from one greeted with skepticism to a now rapidly advancing research field. Actin has now been implicated in transcription by all three RNA polymerases, but the structural form it adopts in these processes remains unclear. Recently, a claim was made that monomeric nuclear actin plays a role in signal transduction, while a just-published study of RNA polymerase I transcription has implicated polymeric actin, consorting with an isoform of its classical partner myosin. Both studies are critically discussed here, and although there are several issues to be resolved, it now seems reasonable to start thinking about functions for both monomeric and assembled actin in the nucleus

“Tall oaks fallen”: Three Pioneers of Chromosome Science

“As when, upon a tranced summer-night

Nuclear actin extends, with no contraction in sight

Within the past two years, actin has been implicated in eukaryotic gene transcription by all three classes of RNA polymerase. Moreover, within just the past year, actin has been identified as a constituent of filaments attached to the nuclear pore complexes and extending into the nucleus. This review summarizes these and other very recent advances in the nuclear actin field and emphasizes the key present issues. On the one hand, we are confronted with a body of evidence for a role of actin in gene transcription but with no known structural basis; on the other hand, there is now evidence for polymeric actin--not likely in the classical F-actin conformation--in the nuclear periphery with no known function. In addition, numerous proteins that interact with either G- or F-actin are increasingly being detected in the nucleus, suggesting that both monomeric and oligomeric or polymeric forms of actin are at play and raising the possibility that the equilibrium between them, perhaps differentially regulated at various intranuclear sites, may be a major determinant of nuclear function