Fragment encoding amino acid residues 30-120 of the Homo sapiens CDT1 gene (HGNC:24576). This fragment contains the Cyclin-binding motif, but not the N-terminal Cul4 E3 ligase-binding sequence or the GMNN binding region of full-length CDT1. If a protein of interest is tagged with this sequence, it is expected to accumulate in the G1 phase only, due to cell-cycle regulated protein degradation (PMID:18267078).