In eukaryotes, DNA is compacted into chromatin, of which the basic unit is the nucleosome. Nucleosomes are comprised of two copies of each of four histone proteins wrapped by 147 base pairs of DNA. Compacting DNA allows the molecule to fit into cells in an orderly fashion but makes DNA less accessible to cellular machinery such as transcription factors. To overcome this difficulty, histone post-translational modifications and histone variants, among others, maintain chromatin in a dynamic state regulating its accessibility. Thus, genes that are required for cellular processes can be expressed or repressed at the appropriate time. Our research focuses on understanding the mechanisms by which chromatin and its modifications regulate cellular processes. We have two main areas of investigation: the analysis of post-translational modifications of newly synthesized histones and their impact on cellular processes, and the role of the viral chromatin in the replication of the hepatitis B virus.