first cyclin box found in G1/S-specific cyclin-D1 (CCND1)
CCND1, also called B-cell lymphoma 1 protein (BCL-1), or BCL-1 oncogene, or PRAD1 oncogene, is a regulatory component of the cyclin D1-CDK4 (DC) complex that phosphorylates and inhibits members of the retinoblastoma (RB) protein family, including RB1. The complex also regulates the cell-cycle during G(1)/S transition. It is an important cell cycle regulatory protein involved in carcinogenesis of various human cancers. CCND1 contains two cyclin boxes. This model corresponds to the first one. The cyclin box is a protein binding domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",