| EEF1D (eukaryotic translation elongation factor 1 delta) is a noncatalytic subunit of the eEF1 complex that functions as a guanine nucleotide exchange factor component for eEF1A and thereby supports the elongation phase of protein synthesis, where eEF1A delivers aminoacyl‑tRNAs to the ribosomal A site in a GTP‑dependent manner. The protein belongs to the EF‑1β/EF‑1δ family and contains an N‑terminal regulatory region and a C‑terminal catalytic-like domain that associates with other eEF1B subunits (EEF1B2/EF‑1β and EEF1G) to form the multi-subunit eEF1B complex, which catalyzes exchange of GDP for GTP on eEF1A, regenerating the active eEF1A–GTP species for repeated rounds of tRNA delivery. During mitosis, EEF1D is phosphorylated at a conserved cyclin-dependent kinase 1 consensus site within its catalytic domain, which reduces its affinity for eEF1A and decreases the formation of eEF1A–GTP–tRNA ternary complexes, leading to hindered tRNA delivery to elongating ribosomes and contributing to down-regulation of global translation at the elongation step during cell division. EEF1D also exists as at least two isoforms with distinct functions: the canonical isoform participates in elongation factor recycling, whereas an alternative isoform associates with heat shock transcription factors and binds directly to heat shock elements in promoters, supporting induction of heat shock–responsive genes and linking translation machinery components to transcriptional stress responses. Beyond its core role in translation elongation, EEF1D engages with signaling and regulatory pathways; interactions with HIV‑1 Tat alter host–virus translational balance by repressing host mRNA translation while favoring viral protein synthesis, and EEF1D participates in networks associated with PI3K–Akt, PPAR, and AMPK signaling that influence lipid metabolism and secretory function in specialized tissues such as the mammary gland. Dysregulated EEF1D expression is reported in multiple malignancies, including oral squamous cell carcinoma and other solid tumors, where EEF1D is overexpressed and associates with activation of cyclin D1 and vimentin, enhanced proliferation, and epithelial–mesenchymal transition phenotypes, while silencing or interference with EEF1D expression reduces proliferation, invasion, and PI3K/Akt pathway activity and shifts BAX/BCL‑2 balance toward apoptosis. |
