The NF-kB-dependent signaling pathways are essential components of cellular response to stress. Mammalian family of NF-kB consists of five NF-kB/Rel proteins, which are subunits of the NF-kB transcription factor, and four IkB proteins, which are their specific inhibitors. Activation of NF-kB requires degradation of IkB, which allows nuclear translocation of NF-kB and its binding to cisacting DNA regulatory elements. NF-kB transcription factors regulate expression of numerous genes, which are involved in cell proliferation, apoptosis, immune response and inflammatory response.

The rotation of earth around its axis leads to environmental changes in light intensity and temperature that predictably define day-night cycle. Most organisms coordinate their life cycle in anticipation of these environmental fluctuations. The measurement of time and synchronization with the environment are achieved by an internal time-keeping mechanism biological clock. The circadian clock is an endogenous mechanism that generates rhythms with an approximately 24-h period and enables plants to adapt to daily and seasonal changes in their environment.

Pax proteins (called Paired box protein) regulate processes related to the division and differentiation of many cell types during embryonic and postnatal development in different animal species. Pax genes are evolutionarily conserved, their homologs found in the genome of nematodes and insects, and amphibians, fish, birds and mammals. No genes or functional abnormalities of the Pax proteins can lead to malignant transformation. In this paper, the structure and functions of Pax factors and their interaction with other proteins.

Glycosylation, consisting in incorporation of single N-acetylglucosamine residues attached by O-linkage to serine or threonine residues, is a common modification of nuclear proteins. Numerous chromatin and nuclear pore complex proteins as well as RNA polymerase II and some transcription factors are glycosylated in this unusual way. O-glycosylation of nuclear proteins has been postulated to play a role in nucleus-cytoplasmic transport, transcriptional regulation and regulation of protein phosphorylation level.