The Caston lab at CSIC





Lab of Viral molecular machines

Head: José R. Castón, Ph.D.


Our studies address to elucidate structure-function-assembly relationships of viral macromolecular complexes, also known as viral nanomachines, which control many fundamental processes in virus life cycle. Our model systems of viral molecular machines are the viral capsid and other viral macromolecular complexes, such as helical tubular structures and ribonucleoprotein complexes. We are investigating several viral systems with different levels of complexity: double-stranded (ds)RNA viruses such as infectious bursal disease virus (IBDV), Penicillium chrysogenum virus (PcV) and human picobirnavirus (HPBV), and single-stranded RNA viruses as human rhinovirus 2 (HRV2) and rabbit hemorrhagic disease virus (RHDV).

The structure of regular viral capsids, in which capsid proteins make extensive use of symmetry, is a paradigm of the economy of genomic resources. Capsids should not be considered as inert closed structures but as dynamic structures, defining different functional states, that participate in multiple processes: virus morphogenesis, selection of the viral genome, recognition of the host receptor, and release of the genome to be transcribed and replicated; some capsids even participate in genome replication. Structural analysis of viruses at the highest achievable resolution is therefore essential to understand their properties. We are carrying out nanoscopic studies of these biomachines by single molecule manipulation techniques such as atomic force microscopy (AFM) to correlate structural features of capsomer interactions with their mechanical properties.

To reveal the three-dimensional structure of such complex assemblies we use hybrid methods that combine cryo-electron microscopy and image processing techniques with high-resolution X-ray structures. Our studies intend to establish the molecular interactions of the components in these complex assemblies, as well as the molecular basis of their functional implications. We have incorporated state-of-the-art approaches to obtain near-atomic resolution structure directly from two-dimensional micrographs.

We are also focused in the study of the structural basis of dsRNA virus replication. All dsRNA viruses, from the mammalian reoviruses to the bacteriophage phi6, including fungal viruses, share a specialized capsid involved in transcription and replication of the dsRNA genome.