Currently browsing: “Alejandra Loyola”

Marking Histone H3 Variants: How, when and why?

KEYWORDS: 2007 • Alejandra Loyola

ABSTRACT: DNA in eukaryotic cells is compacted into chromatin, a regular repeated structure in which the nucleosome represents the basic unit. The nucleosome not only serves to compact the genetic material but also provides information that affects nuclear functions including DNA replication, repair and transcription. This information is conveyed through numerous combinations of histone post-translational […]

PTMs on H3 variants before chromatin assembly potentiate their final epigenetic state

KEYWORDS: Alejandra Loyola • Chromatin Assembly • Epigenetic State • genome • H3 Variants • Histone posttranslational modifications • PTMs

ABSTRACT: Histone posttranslational modifications (PTMs) and sequence variants regulate genome function. Although accumulating evidence links particular PTM patterns with specific genomic loci, our knowledge concerning where and when these PTMs are imposed remains limited. Here, we find that lysine methylation is absent prior to histone incorporation into chromatin, except at H3K9. Nonnucleosomal H3.1 and H3.3 show distinct enrichments in […]

Histone chaperones, a supporting role in the limelight

KEYWORDS: Alejandra Loyola • Asf1 • CAF-1 • Genevieve Almouzni • Hir/Hira • Histone chaperone • Nap-1 • Nucleoplasmin

ABSTRACT: In eukaryotic cells, highly basic histone proteins are associated with the DNA to form the nucleosome, the fundamental unit of chromatin. Histones are closely escorted by histone chaperones from their point of synthesis up to their delivery site. We will present an overview of the histone chaperones identified to date with their various roles, in an […]

Bromodomains in living cells participate in deciphering the histone code

KEYWORDS: acetylated histones • Alejandra Loyola • amino acids • Bromodomains • chromatin-associated proteins • deciphering • histone code • Interactions • N-terminal

ABSTRACT: The bromodomain, a module of  ~110 amino acids, is found in several chromatin-associated proteins, including histone acetyltransferases and chromatin-remodeling factors, and can bind to acetylated lysines. Such post-translational modifications occur mainly in the N-terminal tail of the histone proteins and, in combination with other modifications, are thought to participate in defining a histone code. Recent findings provide a model for how bromodomain-containing […]

The Constantly Changing Face of Chromatin

KEYWORDS: advancements • Alejandra Loyola • ATP-dependent • chromatin • DNA • H2A • Histone Variants • nucleosome • Nucleosome Structure: • proteins

ABSTRACT: Many recent findings have altered our vision of chromatin and its role in the regulation of cellular functions. Our perspective concerning chromatin has changed to a much more complex, but also more dynamic, view of chromatin as an entity that is intimately involved in the regulation of a variety of cellular functions. In this review, we describe the various types of […]

Functional Analysis of the Subunits of the Chromatin Assembly Factor RSF

KEYWORDS: acidic protein • Alejandra Loyola • cDNA • Chromatin Assembly Factor RSF • cloning • eukaryotes • HBXAP • ISWI-containing • nucleosome • Rsf-1

ABSTRACT: The human ISWI-containing factor RSF (for remodeling and spacing factor) is composed of two subunits: the ATPase hSNF2H and p325 (Rsf-1), a protein encoded by a novel human gene. We previously showed that RSF mediates nucleosome deposition and generates regularly spaced nucleosome arrays. Here we report the characterization of the largest subunit of RSF, Rsf-1. We found […]

Histone deposition and chromatin assembly by RSF

KEYWORDS: Alejandra Loyola • Chromatin Assembly • DNA • H2A • H2B • H3 • H4 • Histone deposition • Histones • Purification • Recombinant chromatin • Remodeling and spacing factor (RSF)

ABSTRACT: It is becoming clear that the structure of cellular chromatin is dynamic and capable of undergoing rapid changes to respond to the metabolic requirements of the cell. These changes have a direct impact on gene expression and, therefore, the chromatin context must be considered when biochemical reactions that involve DNA are studied. Over the past several […]

Facile synthesis of site-specifically acetylated and methylated histone proteins: Reagents for evaluation of the histone code hypothesis

KEYWORDS: acetylation • Alejandra Loyola • genetically encoded • H2A • H2B • H3 • H4 • histone code • histone proteins • methylation modifications • peptide synthesis

ABSTRACT: The functional capacity of genetically encoded histone proteins can be powerfully expanded by posttranslational modification. A growing body of biochemical and genetic evidence clearly links the unique combinatorial patterning of side chain acetylation, methylation, and phosphorylation mainly within the highly conserved N termini of histones H2A, H2B, H3, and H4 with the regulation of gene expression and chromatin assembly […]

Reconstitution of recombinant chromatin establishes a requirement for histone-tail modifications during chromatin assembly and transcription

KEYWORDS: Alejandra Loyola • CHRAC-14 • CHRAC-16 • Chromatin Assembly • histone-tail • ISWI-containing • Nap-1 • Recombinant chromatin • Reconstitution • remodeling • transcription

ABSTRACT: The human ISWI-containing factor RSF (remodeling and spacing factor) was found to mediate nucleosome deposition and, in the presence of ATP, generate regularly spaced nucleosome arrays. Using this system, recombinant chromatin was reconstituted with bacterially produced histones. Acetylation of the histone tails was found to play an important role in establishing regularly spaced nucleosome arrays. Recombinant chromatin lacking […]

Purification and characterization of a human factor that assembles and remodels chromatin

KEYWORDS: Alejandra Loyola • Assembles • ATP-dependent • Characterization • chromatin • Chromatin Assembly • hSNF2h • Human Factor • nucleosome • Purification • Remodels

ABSTRACT: We have previously reported the isolation and characterization of a nucleosome remodeling and spacing factor, RSF. One of the RSF subunits is hSNF2h, a SNF2 homologue. Here we set out to isolate and characterize other hSNF2h-containing complexes. We have identified a novel hSNF2h complex that facilitates ATP-dependent chromatin assembly with the histone chaperone NAP-1. The complex possesses ATPase activity that is […]