Table 1.

Cell cycle reporters for use in mammalian cells.

Reporter	Pattern		Advantages	Considerations
PCNA (or PCNA nanobody [55])	G1	diffuse nuclear	DNA replication sensor Single fluorescence channel for all phases (time lapse only) high-contrast S/G2 transition marker	requires high resolution images requires regular nuclear morphology and monolayer culture subtle G1/S change
	S	punctate
	G2	diffuse nuclear
	M	diffuse whole cell
Cdt130-120 (or Cdt116-120)	G1	increasing	SCFSkp2 activity sensor	requires T or E in linker (at 29) slow degradation in S phase very sensitive to reporter expression levels
	S	peaks after G1/S
	G2	low
	M	low
PIP	G1	stable	DNA replication sensor single fluorescence channel for all phases (time lapse only) high-contrast G1/S marker insensitive to reporter expression levels	absent in S phase (requires 2nd marker for automated tracking) sensitive to high levels of exogenous DNA damage in G1
	S	absent
	G2	increasing
	M	diffuse whole cell
Geminin1-110 (or Geminin 1–60)	G1	absent	APC activity sensor distinguishes S and G2 from G1 Geminin1-60 labels cytoplasm (cell shape)	unreliable marker of S phase entry somewhat sensitive to reporter expression levels
	S	increasing
	G2	increasing
	M	decreasing