SYSARTICLECOL system table

CREATE TABLE SYS.SYSARTICLECOL (
	publication_id	 UNSIGNED INT NOT NULL,
	table_id	 UNSIGNED INT NOT NULL,
	column_id	 UNSIGNED INT NOT NULL,
	PRIMARY KEY (publication_id, table_id, column_id),
	FOREIGN KEY REFERENCES SYS.SYSARTICLE,
	FOREIGN KEY REFERENCES SYS.SYSCOLUMN
)

Each row identifies a column in an article, identifying the column, the table it is in, and the publication it is part of.