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The homeotic proteins are transcription factors, highly conserved in metazoan organisms, exerting a pivotal role in development and differentiation. They individually display a loose specificity for the DNA sequence they can bind, but operate mainly in multi-molecular associations that assure their target and function specificity. Homeotic proteins are known to play a role in the positive or negative regulation of cell proliferation. Furthermore, many homeotic proteins are actually proto-oncogenes, since different translocations involving their genes cause tumors, particularly in the hematopoietic system. A one-hybrid screen to detect proteins with affinity for the lamin B2 replication origin identified three homeotic proteins, namely HoxA13, HoxC10 and HoxC13. Recent data demonstrate that the HoxC13 oncoprotein specifically associates with replication foci and binds in vitro and in vivo to several human DNA replication origins. Moreover, Hox proteins interact with geminin, a regulator of cell cycle progression, and control the interaction of this protein with the DNA replication licensing factor Ctd1. Thus, the homeotic proteins, by participating directly in the function of DNA replication origins, may provide a direct link between the accurate regulation of DNA replication required by the morphogenetic program and the deregulation of this process typical of cancer. [ABSTRACT FROM AUTHOR]

Presents data which show that the arrangement of tRNA in the ribosome depends not only on which of the two mRNA codons inside the ribosome binds tRNA but also on the functional and the structural state of the elongating complex. Advantages for the more precise and more detailed classification of the tRNA-binding sites of the ribosome; Interaction with the functional state.

Monomercurated tRNA has been prepared by exhaustive treatment of mercaptoethanol on polymercurated tRNA under non-denaturing conditions. The remained mercury atom is stable toward ultraviolet (254 nm) irradiation up to absorption of 100 quanta/nucleotide, but could be easily removed by mercaptoethanol under denaturing conditions. Monomercurated tRNA quantitatively binds to thiopropyl-Sepharose and can be completely desorbed by mercaptoethanol-containing solutions. Monomercurated tRNA is similar to the starting tRNA preparation in efficiency and specificity of aminoacylation and in factor-dependent polypeptide synthesis in vitro. [ABSTRACT FROM AUTHOR]

Studies the efficiency and specificity of RNA-protein cross-linking in the 30S subunit of Escherichia coli ribosomes induced by low-intensity and high-intensity photons. Observations of biphotonic processes in the high-intensity photon environment; Efficiency of cross-linking is 20-100 higher upon two-step excitation compared with single-step excitation.