1. Introduction
  1.1 Background
  1.2 Objectives
2. Protein Ubiquitination: Overview and Significance
  2.1 Definition and Types of Ubiquitination
  2.2 Ubiquitin-Proteasome System
  2.3 Roles of Protein Ubiquitination in Cellular Processes
3. Enzymatic Machinery of Protein Ubiquitination
  3.1 E1 Enzymes: Ubiquitin-Activating Enzymes
  3.2 E2 Enzymes: Ubiquitin-Conjugating Enzymes
  3.3 E3 Enzymes: Ubiquitin Ligases
  3.4 Deubiquitinating Enzymes (DUBs)
4. Regulatory Mechanisms of Protein Ubiquitination
  4.1 Ubiquitin Chain Assembly and Linkage Specificity
  4.2 Ubiquitin Ligase Regulation
  4.3 Deubiquitination and Ubiquitin Recycling
5. Functional Consequences of Protein Ubiquitination
  5.1 Protein Degradation and Proteasomal Pathway
  5.2 DNA Repair and Genome Stability
  5.3 Signal Transduction and Cell Signaling Pathways